Users can see a black screen for a variety of reasons.
When you update VMware Tools, the update can in some cases install the wrong video driver, resulting in black screen. The workaround is to log into the session using RDP and install the correct driver.
If the System Administrator moves a desktop from a non-PCoIP pool to a PCoIP pool and users experience a black screen when trying to connect to the desktop, solutions can be found in the VMware Knowledge Base.
Refer to the steps outlined in the VMware Knowledge Base article Black screen when logging into a VMware View virtual desktop using PCoIP.
Verify that the Video RAM (VRAM) settings in the Virtual Machine settings (.vmx) file are set properly for multi-monitor access when using the PCoIP protocol. Refer to the VMware Knowledge Base article Determining display and screen resolution settings for PCoIP.
Verify that the Video driver is correct for the VMware View Agent and operating system. Refer to the VMware Knowledge Base article "The PCoIP server log reports the error: Error attaching to SVGADevTap, error 4000: EscapeFailed."