When you try to connect to a server, PowerCLI checks whether the server certificate is valid. You might have to configure the PowerCLI settings to be able to connect to servers with untrusted certificates.
You might not be able to connect to a server because of the default action configured for PowerCLI and untrusted certificates.
By default, PowerCLI is set to deny connections to servers with invalid certificates. You can retrieve the current setting for invalid server certificates, and configure it as required. For more information, see Configure the PowerCLI Response to Untrusted Certificates.