Appointment+ Locations don't work

I have installed Appointment+ and I have activated the add-ons for locations and service locations. However, as you can see in the attached screenshots in the Locations tab I am not able to add new locations (i.e. there is no button for that). Also, the Edit Locations and Settings in the same tab they don't work at all. My site is a multi-site installation but I am working at a specific site only.

Please, advise what I am doing wrong.