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Could you please share a bit more about the error message on your side?
I have made a test on my side, and don't have the issue that you mentioned.
Please take a try to clear cache of your browser and re-start your machine, then try it again, check if the issue is solved.
In addition, please make sure that your sign in account is a Work or School account rather than a Personal account. Currently, Personal account is not allowed to sign in PowerApps.
Please also check if your sign in account (Office 365 account) has been disabled from your Org.