@Juan Carlos González Martín 

Ramiro's teacher told to her students that at the beginning you need different user for educa.madrid.org than for Teams, but now it is the same one.

It looks like that Teams recognize eduga.madrid.org as organization, you can check trying to reset the password, the page has the flag of Comunidad de Madrid, and it answers to you that this organization doesn't permit to reset it.

A part from that there is a form to request help here: https://forms.office.com/Pages/ResponsePage.aspx?id=TrLhm6C2t028DNMzJWa_M9xpwjIT9HBFg-YJHifbGA1UQjlW...

But you don't receive anything at your educa.madrid.org mail telling you that a ticket is open, and also the problem persist, probably because there isn't a proper suppport service in place, yet.