iPhone photos not uploading to iCloud

I routinely download my camera roll from iCloud to my pc hard drive as the phone is not recognised as a drive these days. I’ve noticed that about a hundred holiday photos haven’t been uploaded to iCloud. On investigation I find in the information below the photos that there is a cloud symbol with a strike through it. I haven’t purposely altered any settings and later photos have uploaded ok. Is there any way I can switch the uploading back on for the affected photos, or is there a way of saving them which would change the setting?