various problems after setting up M365 Business (due to upgrading Teams)

Hello everyone I set up a new Microsoft tenant in a small company. You haven't had your own tenant yet (at least nobody has used it) but you've been using Teams Free. When I created the tenant and set up the domain, 4 of the 8 users already appeared in my active users. I suspected this was because you were already using Teams. I then set up the remaining users and assigned the licenses (Microsoft 365 Business Standard). Now I have different problems. I was able to register the Microsoft account for the Office license with one user. If I now want to register his company account with OneDrive, I get the error: AADSTS50020 User Account from identity provider does not exist in tenant and cannot access application When I log in to onedrive.com with his account, it works. With another user, when I log into Word, I get the message that the user does not have an Office license. I've checked several times, the license is assigned correctly. What I've seen is that some users with the company address have a personal and a company account with Microsoft. I then changed the login address in the private accounts and removed the company email address, but that didn't help. Has someone a tip for me? I've already set up a few tenants, but I've never had this problem.