Same here it worked just fine yesterday and it suddenly turned off today. I tried editing the PROFSAVE_profile file to force enable DLSS and it doesn't work even when set to read-only. It's quite annoying as the TAA in the game is quite inferior to DLSS
Ok so I tried to replace the DLSS .dll with the same 3.11.1.0 .dll with DLSS Swapper and it fixed the issue. I then tried to delete the DLSS .dll and verified the files on the Steam and it still works even with original DLSS .dll.
So maybe try to delete nvngx_dlss.dll in your game directory and then verify the files on Steam, if that doesn't work use DLSS Swapper to swap DLSS with the same version
