Depends on what you mean with not working. Get any errors? e.g. i like to test with vkcube. if gamescope vkcube runs, then its likely not a gamescope problem but one with the e.g. game you try to run or wine / proton.

The latest versions seem to be indeed a bit problematic. The last that works (mostly) flawless on my Arch is 3.14.2. So maybe worth a shot to downgrade to that if your current one fails with vkcube.

Otherwise, it is probably a good idea to get in contact with the Nobara community or the developer. I hate to recommend Discord, but as far i know that is unfortunately where they are active.