Fallout 3 and Fallout New Vegas through Backwards Compatiblity on Series X and Xbox One not...

I recently got a Series X console and tried to play Fallout 3, but it keeps giving errors about not being able to connect to Xbox Live, even though the console has an internet connection and I'm already signed in. I've tried deleting and redownloading my 360 profile to the Series X, but it gives a different error about a problem with the credentials I entered, and fails to redownload the profile. Sometimes it will give this error immediately after entering my email and app password, and other times it will almost finish downloading my profile, but get stuck on "downloading avatar files", then fail and show this error. The wording of the error is: "Sorry, there was a problem with the credentials that you're using to sign in. Go to account.live.com to fix the problem. 80151015". I've tried searching for that error code and found nothing helpful.

Clearing the 360 local files from the storage settings on the Series X didn't help either, and in fact caused the same problem to start happening on my Xbox One as well when I did the same thing on that console, thinking that it might help. I had read about others with this problem saying that deleting the 360 files from their Xbox One had solved this issue on their Series X, but I now have this same problem on both consoles.

I've tried other 360 games like Dark Souls, Skate 3, and The Elder Scrolls Oblivion, and they all work perfectly on both Xbox One and Series X. So far I've only had this problem with Fallout 3 and Fallout New Vegas. This problem also occurs when I try to play these 2 games through Xbox Cloud Streaming as well.

Now the only way I can play these 2 games is on an Xbox 360 console. Signing in to my profile on my 360 console works fine and the games start and play normally, but it's disappointing that I can't play them on my newer consoles now.

This is also affecting my sister's xbox profile as well, same errors with the same games, on the same consoles.

Any help solving this would be appreciated.

:)