Bookings link not working - starts Outlook page

On our Office 365 E3 license we have added the bookings app. It shows properly on the panel. However, when clicking on this link it does not start the bookings page but only outlook.office.com.

This behaviour is the same on safari or chrome. It is also the same behaviour on the admin account and on the employee account. We have used the bookings app to set the bookings app - which works fine.

thank you 

uli