Msfs won't start since going from DX12 to DX11

The issue will occur even without the use of the NVIDIA app (not installed). I just had this issue with no NVIDIA app installed. I had to do an uninstall of GPU drivers the used DDU and reinstalled 580.88 drivers without NVIDIA app. It occurs with use of switching from DirectX 11 to 12 then back.

My suggestion once you install the GPU drivers do not switch from DirectX 11.