I was helping someone with teams earlier. The usual story, important meeting coming up and they wanted to make sure it's going to work alright on the night (or day as the case may be).
They have the email link ready to test - click the link - no welcoming message, no. Your admin hasn't enabled teams!
But who is the admin? Not to worry, there's some button here that says sign up for free - well, you can't go wrong with free can you? So ignore the webpage title indicating it's for commercial access (who reads titles anyway?) and... what's this? You already have teams with your account! Well, that was easy I guess, take me to my free teams then...
Oh, we're now back to the "your admin hasn't enabled teams" message.
Okay, let's do a quick search on the internet for... oh dear, I seem to be getting loads of pages about the admin centre on Microsoft 365... but this is not a large enterprise, it's a personal account wanting to use teams for an important meeting they've been invited to - why isn't this simple?
Lots of head scratching - as it happens, I wasn't the first to encounter this issue - they had sought help from others already, and worse yet, other people had fixed it - it came up with the correct view when clicking on the link, but the moment they got back home and tried it again just to be sure, back to the message, your admin hasn't enabled teams...
So what could it be - why did it work for some yet not for the person who needed it the most?
The answer it turns out, is that teams decided it needed to load on start up.
So when the computer is booted, teams launches... it prompts to sign in. The user signs in, and for whatever reason, teams now thinks it's in commercial use mode, and you're not allowed to join a meeting because your "admin" hasn't enabled something.
Yet if you sign out of the account, close teams, and then click the link, it opens up fine. Better yet, disabling its paradoxical startup entry prevents the whole issue occurring in the first place.
I haven't used teams for meetings myself, but my goodness what a convoluted mess of a system. If someone wants to join a meeting, why should it matter if they signed into teams (with a non-microsoft email account I might add, not a workplace email with outlook or any other nonsense) because teams decided it's a good idea to run at startup without even asking first?
At least Zoom allows you to set up a free account and host meetings for free without any difficulty, or join meetings effortlessly whether you're signed into the app or not (which also doesn't throw itself into startup to slow down an already overloaded operating system).