Photos imported via webinterface cannot be edited on iOS devices
I can confirm that this is not a blanket restriction and I have uploaded some images via iCloud (tested a PC / Windows 10 and macOS Catalina) web app.

I would upload an image that isn’t already in your library as a duplicate as I believe the system is trying to match duplicates.

Once that’s done, you will likely need to wait out whatever processing is stuck on your specific library or engage Apple support since they would need to look server side to investigate why specific images are stuck.

Expect to spend at least 30 minutes on the phone with Apple to collect information and/or try the “FAQ” steps and eventually if there isn’t a workaround or quick fix, you’ll be asked to make a support PIN to engineering or higher tier iCloud support can look at your specific sync data.


https://support.apple.com/en-us/HT202650