Apple Photos App Full (without pictures)

I kept getting an error message on the Apple Photos app on iPhone and on Mac saying my "iCloud is full," so I just deleted the pictures and it kept giving the same error. There are now no pictures whatsoever in my library but I keep getting the same error and when I look on my iCloud settings to see what is taking up so much space it says 2.8GB of it is photos, even though they're all gone and they're even all deleted from the "recently deleted" section. I've been having to use Google Photos for the time to back up photos, which I'm not a big fan of, but I feel they need to be backed up someway.

How can I get this fixed so I can go back to using the the Photos app?

Any help would be great!