Hi @Carlos Agustín López Aguilar ,
Your issue is covered your privacy information, so we edited your part of description. Thanks for your understanding!
Regarding to your issue, it seems your account is not in the tenant now. In this case, we recommend you contact the Teams admin to check if they have added you in Teams as guest user from Azure Active Directory side. To check this, Go to Azure Active Directory portal > Users > Check you are added as a guest user or if you are not there, ask them to added your user account as Guest user and then check the result.
Also, please make sure if they have enabled guest access and external access from their end. They can check this setting from Teams Admin center > Org-wide settings > Guest and External access.
If the response is helpful, please click "Accept Answer" and upvote it.
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.