Some Photos not syncing to iCloud

I imported some photos into the macOS (version 10.14.6) Photos app .

For some reason, those photos are not syncing to iCloud and do not show up on my iPhone 12 (OsX 14.6).

iCloud Photos option is ON in macOS Photos and also ON in the settings for Photos on the iPhone.

I also checked on my icloud.com account and the imported photos are not there either.

Why ?

Thanks for your help.