cant login to free version of microsoft teams: redirect to https://teams.microsoft.com/_#/licenseErr

Hello together,

my problem is that my organisation is not able to login via webclient and desktop app to the free version of teams. we are always getting a redirect to this link: https://teams.microsoft.com/_#/licenseError?errorCode=GuestUserNotRedeemed

hope there is someone who can help us.

thanks