Everytime I try to open a new Quiz/Form, I get "Your account is not activated for Microsoft Forms"

Hello,

I have a work account for Office365. I can log in to Microsoft Forms after the admin of my organization gave me permission for Forms and I see the usual interface. However, at the moment of opening a new quiz/form, I can see a Form created for one second and afterwards the screen changes to "Your account is not activated for Forms. Please contact your admin." (see below, equivalent in German)

How can this problem be fixed?

Thanks in advance!