Checking through the community, a few start up issues have appeared in relation with 5.6. Particularly, the error you are getting is tied to GPU issues, either software or hardware:
D3DCommandQueue->GetClockCalibration(…) failed with error E_FAIL
Let’s cover a few methods for resolution:
Refresh your nVIDIA drivers. Pick the “Clean Installation” option, as well as going for the “Developer” drivers, as these have more stable settings for engine work
Test switching between DX11 and DX12
Go to Windows Graphic Settngs, and set UE to High Performance
Since you recently updated to UE 5.6, try deleting all files from directory C:\Users\UserName\AppData\Local\UnrealEngine (make a backup just in case)
Access regedit, navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\GraphicsDrivers, and add a TdrDelay at value 60 (this will prevent the engine from “losing” your GPU)
Ensure your GPU is properly mounted, and no connection is lost with your motherboard
switching to dx11 should work. create a shortcut to ue5.6 and append " -d3d11" to target. Idk why its happening. I have Ryzen 3 3250u , up until now no problems but 5.6 crashes on startup if its dx12. Hope they fix it soon!