McDonald’s app

If you created a McDonald's account with Apple's. "Sign In with Apple" Feature,

What is Sign in with Apple? - Apple Support

it could be possible something is broken on Apple's end. Might be worth asking Apple Support if you created any McDonald's accounts using your Apple ID by calling them up to see if maybe that's what you're ultimately facing.

Contact McDonalds for help with their software.

How to contact an app developer - Apple Support

Good, hopefully they can fix this for you.