Not all photos are uploaded from PC to iCloud Photos
My PC (Windows 11) iCloud photos folder were synced with iCloud. Around 11k photos. I proceeded to copy around 8k photos and videos to the iCloud photos folder and left it overnight to sync. In the morning the iCloud status on the PC was that all files were uploaded. However, the number of photos and videos on PC were 19k while iCloud had only 14k leaving 5k photos missing from iCloud. I checked my iPhone as well as iCloud.com and the pictures are not there.
What could cause this to happen?