My cousin’s husband’s iPhone was not uploading his photos to iCloud Photo Library. It was a bit of a head scratcher because it wasn’t an Apple server issue because my iPhone was uploading my photos at the same time I was troubleshooting. I tried rebooting his phone, closing the Photos app.
I caved and looked it up on the interwebs and I found a solution on the Apple Support Communities site. He had less than 300MB and photos and videos will not upload if you have less than that. Odd but removing some photos and apps he didn’t use worked and his photos started to upload.