I visited the official website of GearPlayer and found out a lot of stuff about it including the system requirements that you need.
Microsoft Windows Vista, Windows 7, Windows 8 or Windows 10 Operating System
Microsoft Internet Explorer 11 or newer (Microsoft Edge)
Microsoft Windows Media Player 11 or higher (for CODEC support)
Microsoft.NET 3.5 Framework
As you can see Windows terminal server doesn't appear to be supported and based on what you've said it appears that you're trying to run the application on Windows Server OS. It might work, but make sure to apply a compatibility tweak, even if you're running it on a server.