If you are getting that error on a website you do not own or have the ability to change, you need to report the bug to the admins for that site. They need to fix their redirect URI in Azure or in their code and make sure that it matches. You could reach out to @McDonalds on Twitter and report this issue.
It does look like their website is having issues because I tried to go to the "Help" page and got an ERR_CONNECTION_TIMED_OUT
You can try logging in using an incognito/private window to see if you get a different response, but the reply URL error means that they have a mismatched or incorrectly formatted reply URL configured on their end.
You also may be able to get some help on their Subreddit page: https://www.reddit.com/r/McLounge/comments/dwoaex/hello/