Can’t figure out why iCloud Photos still says sync pending

I am only using 50% of my storage plan, I have really fast fiber internet. I read where it was stated that you could force a sync by signing out of iCloud on the PC and iPhone and restarting. But when I go to sign out I get a warning on the respective devices that they will be wiped of all the photos , obviously not what I want. How hard is it to get all the photos on the phone to go to the cloud and the PC, all photos on the PC to go to the cloud and phone, and all photos on the cloud to be stored also on the PC and phone? It’s almost 6000 photos so it’s really hard for me to go photo by photo and see whether they’re missing from the PC or the cloud or the phone.