Hi there! My name is David. It’s a pleasure to help you today.
Regarding your issue, based on what you've described, you've already tried several solutions without success.
You can try the following:
Go to Settings > Accounts > look for the Other Users option > click on Add account > choose I don't have this person's sign-in information > click on Add a user without a Microsoft account (to create a local account) > in Username, you can enter any name, the password is optional > click Next > click on the newly created account > click on Change account type > select Administrator > click OK.
Sign in to the new account and test the Game Bar. If it works correctly, there may be an issue with the previous user account.
Let me know if the shared information has been helpful. Regards.