Cannot Login to Teams invitation

I have registered for Teams today with my Microsoft Outlook.com ID and when i try to open a link from an Invitation to Teams i have received i got the Message: Login with My Personal Account is here not possible and i need Business Account. Can you tell me what is wrong?

Background we are a Clinic in Switzerland and have MS Products everywhere but this one Laptop is not integrated in the Domain and we just need it to communicate with Teams with Companies like Novartis.

Is it really that complicated? Before we registered it seemed to work. Funny

Thanks for your help, Microsoft Support forwarded me here, i was like WoW.

Best Regards

Pedro