Forgot to mention, but I have also raised the issue through email with case ID: 102669467940. But this post has additional information that was not in the email.

Hello! It seems like we might be facing similar issues where our TestFlight and Appstore applications cannot be downloaded, using the same OS version of Mac as well. Have made a post earlier regarding this issue as well, but so far no one has replied: https://developer.apple.com/forums/thread/797150 Gonna leave a boost so that someone from Apple can take a look at this issue soon! :(