We are experiencing weird issues with 2 different customers that are using Teams for MAC.
The first user, when creating a new meeting in Teams for MAC, cannot invite addresses from within her own organisation. So, UserA@companyA.com cannot invite UserB@companyA.com. Any other address is fine, including e-mail addresses that do not exist.
The second user, from another company entirely, is experiencing the same issue, but reversed. She cannot invite external addresses, only internal.
I'm leaning toward this being some kind of setting, but I am not sure where to look.