Windows 11 admin problems

I’m getting to the end of my tether trying to deal with an IT issue and was wondering if anyone on here can point me in the right direction (I am not an IT person). I have tried multiple searches but none of the answers actually address the problem.

After resetting a Windows 11 laptop and logging in using a Microsoft 365 account, I cannot instal software because I don’t have admin rights. If I provide the Administrator password, it doesn’t accept it. If I log in as Administrator, I can’t see the other user account to grant it admin rights. It’s almost as if I have 2 different machines. What is going on here?