Teams AADSTS900144

Hi, For a few days now, I've been having trouble logging into my company guest account with my personal Microsoft Teams account. Message: AADSTS900144: The request body must contain the following parameter: 'login_hint'. I log in to Teams with my personal account. Everything works. I try to switch to the guest account. It doesn't work. I've tried clearing the cache, removing the account from Windows, deleting SSO, etc. Unfortunately, no improvement. Re-inviting me to the Azure tenant has no effect. Everything works perfectly in the browser. Does anyone have any ideas? Teams isn't a custom application.

Best regards, Marco