Deleted Photos to reclaim iCloud space but none reclaimed
Do you have any other devices using the same library?

I did similar thing last night, deleted some things from my Mac from the library (large video files, around 800mb), and then went to iPhone to check the free storage on iCloud, it wasn't changed.  And my 'Recently deleted files' was empty as well.

Then I opened the Photos app on iPhone, and I could notice the 'pop', the thumbnails moved, so it seems the iPhone synced that those videos are deleted, and after that when I checked the iCloud storage, free storage was increase. 

So, try to open Photos on other devices to let them sync.