Hi @García, Gabriel
Please make sure your device’s date and time are not correct firstly, which can cause the authentication token to expire. Next it is recommended that restart the computer to supply a new modern authentication token and try to sign in again. Sign out, and then sign in again using the old (or incorrect) credentials. After it fails, enter in your correct credentials. Open Microsoft Authenticator app, delete all accounts, open the navigation bar/hamburger menu (upper left) > Settings > Device Registration, and log-in to your account. Close the Teams app and the authenticator application. Then open only the authenticator and wait until Face ID has authenticated you and you can see your accounts. Then open the Teams application and it should work again.
If none of them work, you can contact Global Customer Service phone numbers.
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