Hello Rui Silva,
Thanks for your question.
In some cases, you might already have an active session that uses a personal account than the one that's intended to be used. So it may be signing in to the wrong tenant.
I will recommend you try to sign in using an Edge browser in private mode, that might clear the session. If that doesnt fix, I will recommend you follow the guidance from MS.
The general guidance is here:
You can mark it 'Accept Answer' and 'Upvote' if this helped you
Regards,
Abiola