Missing category selects on left side and Scan Now button not working.
Just check again and looks like this has been resolved. Plus a new update has been posted for CCleaner,
When this happen it’s because the ccleaner 7 windows service has stopped, to solve it (next time)
Exit ccleaner
Press win+r
Type services.msc
Find the ccleaner 7 service (they should be alphabetical)
Make sure it’s set to automatic
Right click the service and choose start
Assure it is running
Open CCleaner