Hello,
Verify your CAP and RAP settings in your Gateway (if applicable), inspect your collection in the connection broker, and RD Web. Open the Event Viewer (Application and Services Logs - Microsoft-Windows), review all logs beginning with TerminalServices and RemoteDesktopServices. Examine the Application and System logs. If any errors are present, investigate further.
If the Answer is helpful, please click "Accept Answer" and upvote it.