Can't change service availability???

Does anyone know how to fix this issue. I am trying to create a bookings page, and for some reason I cannot edit the general availability in the tab 'Booking Page' as well as within individual services.

It is just stuck on 'Not Bookable' or 'Bookable when staff are free'.

I want to change it to customised time slots but when I click on custom hours it just doesn't accept it.

This is an issue on new pages as well as old pages I have previously set up.