ThinApp Packages Fail to Launch from the User Portal

When a user tries to launch a ThinApp package from the user portal, a browser message might appear that prompts the user to download and install the Workspace ONE Access Desktop application even when the application is already installed and running.

Problem

After installing the Workspace ONE Access Desktop application, when the user opens the user portal in a browser on that Windows system, logs in, and tries to launch a ThinApp package, a message might appear stating that the Workspace ONE Access Desktop application must be installed on the system, and prevents the ThinApp package from starting. This message might appear even when the Workspace ONE Access Desktop application process is running on the Windows system. The Workspace ONE Access Desktop application might report that all files are up to date.

Cause

This problem can occur for multiple reasons.

Cause	Description
The Workspace ONE Access Desktop browser plugin is not properly installed or it is not activated in the browser window for the browser in which the user is trying to launch the ThinApp package.	Because installation of the Workspace ONE Access Desktop application is required to run ThinApp packages on the Windows system, the user portal uses a browser plugin to verify whether the application is installed before launching the ThinApp package from the user portal. When the user clicks the icon for a ThinApp package in the user portal, the Workspace ONE Access Desktop browser plugin checks to see if the application is installed before launching the package. If the browser plugin is not installed and active in the browser, the verification cannot happen, the message appears, and the package does not launch. If there are browser windows open during the Workspace ONE Access Desktop installation process, the browser plugin might not be properly installed for that browser. The browser plugin might become deactivated in the browser if the user disabled the plugin in the browser's add-ons or plug-ins page.
The custom protocol handler used to launch the ThinApp package from the browser has been disabled for the browser in which the user is trying to launch the ThinApp package.	In the Workspace ONE portal, ThinApp packages are represented using a link with a horizon:// protocol. When the Workspace ONE Access Desktop application is installed, the installer registers a protocol handler for that horizon:// protocol. The protocol handler is an executable named HorizonThinAppLauncher.exe, and is registered as a handler by the registry entry HKEY_CLASSES_ROOT\horizon\shell\open\command. When the user tries to launch a ThinApp package from its icon in the Workspace ONE portal, this HorizonThinAppLauncher.exe application is launched. If the user has disabled the use of all protocol handlers in the browser, or disabled the use of the handler for the horizon:// protocol, ThinApp packages will not launch using their icons in the Workspace ONE portal. Some browsers present a warning when protocol handlers are launched and give the user the option to select to execute the protocol handler. One way in which the user might have disabled the use of the horizon:// protocol handler is when the user clicked one of the ThinApp package icons for the first time, when the browser warning dialog appeared to ask for permission to run the protocol handler, the user selected No or a similar choice to prevent the launch, and also selected Remember my selection or a similar choice that prevents the launch for all such links. Because permission to run the protocol handler was not given and is remembered, none of the ThinApp packages launch from the Workspace ONE portal.

Cause

Description

The Workspace ONE Access Desktop browser plugin is not properly installed or it is not activated in the browser window for the browser in which the user is trying to launch the ThinApp package.

Because installation of the Workspace ONE Access Desktop application is required to run ThinApp packages on the Windows system, the user portal uses a browser plugin to verify whether the application is installed before launching the ThinApp package from the user portal. When the user clicks the icon for a ThinApp package in the user portal, the Workspace ONE Access Desktop browser plugin checks to see if the application is installed before launching the package. If the browser plugin is not installed and active in the browser, the verification cannot happen, the message appears, and the package does not launch.

If there are browser windows open during the Workspace ONE Access Desktop installation process, the browser plugin might not be properly installed for that browser. The browser plugin might become deactivated in the browser if the user disabled the plugin in the browser's add-ons or plug-ins page.

The custom protocol handler used to launch the ThinApp package from the browser has been disabled for the browser in which the user is trying to launch the ThinApp package.

In the Workspace ONE portal, ThinApp packages are represented using a link with a horizon:// protocol. When the Workspace ONE Access Desktop application is installed, the installer registers a protocol handler for that horizon:// protocol. The protocol handler is an executable named HorizonThinAppLauncher.exe, and is registered as a handler by the registry entry HKEY_CLASSES_ROOT\horizon\shell\open\command. When the user tries to launch a ThinApp package from its icon in the Workspace ONE portal, this HorizonThinAppLauncher.exe application is launched.

If the user has disabled the use of all protocol handlers in the browser, or disabled the use of the handler for the horizon:// protocol, ThinApp packages will not launch using their icons in the Workspace ONE portal. Some browsers present a warning when protocol handlers are launched and give the user the option to select to execute the protocol handler. One way in which the user might have disabled the use of the horizon:// protocol handler is when the user clicked one of the ThinApp package icons for the first time, when the browser warning dialog appeared to ask for permission to run the protocol handler, the user selected No or a similar choice to prevent the launch, and also selected Remember my selection or a similar choice that prevents the launch for all such links. Because permission to run the protocol handler was not given and is remembered, none of the ThinApp packages launch from the Workspace ONE portal.

Solution

Verify the user has logged in to the Workspace ONE Access Desktop application with the user's Workspace ONE Access user account.
The user signs into the client using the Workspace ONE Access icon in the Windows system tray.
If this problem appears shortly after the application is installed on the system, close all open browser windows, reopen the browser, log in to the user portal, and try launching the ThinApp package.

If the problem appears even after closing the open browser windows and reopening the browser, verify the browser plugin appears in the browser's list of plugins and is active.

Browser	Description
Internet Explorer	For Internet Explorer, a COM server is registered instead of a browser plugin or add-on. To test whether the COM server is installed, create a test HTML file with the following contents and open that file in Internet Explorer. The result tells whether the COM server is installed or not. <html> <script type="text/vbscript"> On Error Resume Next dim objName objName = "HorizonAgentFinder.HorizonFinder" dim obj Set obj = CreateObject(objName) document.write(objName & " is ") if IsEmpty(obj) then document.write("not installed") else document.write("installed") end if </script> </html>
Firefox	Open Firefox's Add-ons Manager by clicking Tools > Add-ons. On the Plugins page, verify the VMware Horizon Agent Finder browser plugin is listed and set it to always activate.
Chrome	Open Chrome's content settings by opening the Settings page and clicking Show advanced settings > Content settings. Click Disable individual plug-ins to display the list of plugins. Verify the VMware Horizon Agent Finder browser plugin is listed and set it to always activate.
Safari for Windows	Open Safari's list of installed plugins by clicking Help > Installed Plug-ins. Verify the VMware Horizon Agent Finder browser plugin is listed. Verify that plugin is activated for Safari.

Verify the registry entry HKEY_CLASSES_ROOT\horizon\shell\open\command exists and has a value that is a path that points to the location of the required protocol handler, named HorizonThinAppLauncher.exe, where the Workspace ONE Access Desktop application was installed on the Windows system.
If the registry entry does not exist, or does not have a value that points to the location where the Workspace ONE Access Desktop application was installed, uninstall the application and reinstall it.
If the registry entry exists and has a value that points to the location of the HorizonThinAppLauncher.exe executable, verify the executable exists at that location and has not been moved or deleted.
If the registry entry does not exist, or does not have a value that points to the location where the Workspace ONE Access Desktop application was installed, uninstall the application and reinstall it.
If the registry entry exists and has a value that points to the location of the HorizonThinAppLauncher.exe executable, verify that the (Default) value for the registry entry HKEY_CLASSES_ROOT\horizon has a Data value of URL:horizon Protocol and that the URL Protocol value for the HKEY_CLASSES_ROOT\horizon entry exists.
If the Data value for the (Default) value of the HKEY_CLASSES_ROOT\horizon registry entry is not set to URL:horizon Protocol, update the Data value to set it to URL:horizon Protocol. If the URL Protocol value does not exist for the HKEY_CLASSES_ROOT\horizon entry, you can create it using a value name URL Protocol and no value data.
Determine if the user disabled the horizon:// protocol for the browser, or if all protocol handlers are disabled in the browser, and if so, enable the protocol handler for the browser as appropriate for your organization's needs.
In most situations, the browsers rely on the settings in the registry for information about the protocol handlers available for that Windows system. For some browsers, when the user clicks a link that is associated with a protocol handler, a dialog prompt appears that asks the user a question such as Do you want to allow this website to open a program on your computer? or This link needs to be opened with an application or a similar statement about needing to launch an external application to handle the link. Typically, the dialog provides the user with the option of not launching the external application and to remember that choice for all links of that type. The steps to re-enable the ability to launch the application associated with the protocol handler are usually different depending on the browser type. Consult the documentation for the user's type of browser on how to enable protocol handlers for that browser type.