I finally decided to migrate my aperture library (33,000 images) to photos. All seemed to go smoothly until I checked “iCloud Photo Library.” I plugged my computer directly into my modem for fastest uploads, and within a few days, the settings pane said “Uploading 1,000 images” which was great news that I was almost finished! The next time I looked at my computer, the “iCloud Photo Library” was UNCHECKED! It’s UNCHECKED itself! It prompted me to upgrade from the 500GB plan to the 1TB plan, even though my library was only 300GB and I had 50Gb available. I upgraded anyway just to see if it would help. Now my computer says Uploading 30,000 images! It started all over again! I have returned to my computer several times over the past few days and the iCloud checkbox is UNCHECKED again! I re-check it, and move on. It keeps happening! Help!