eM Client causes issues with full-screen applications

After installing eM Client, video games like Fortnite and Grand Theft Auto have trouble launching and staying in full screen mode. After killing eM Client through task manager, the games can enter and stay in full screen mode. My desktop resolution is 3840x2160 @ 144hz. The games usually launch and run in 2560x1440 @ 144hz.

Operating System: Windows 10 Home Edition, Version 20H2 (19042.985)
Graphics Card: RTX 2080.
Graphics Card Driver Version: 466.63

That’s very strange. What version of eM Client are you running ?

Also what happens if you run in 2K Res 2560x1440 at the same 144hz ?