I am experiencing the same issue with my daughter's iPhone 7. We upgraded her iCloud account to 50gb, but they 2.6gb of photos that were on her iCloud account before the upgrade remains the same. There is no indicator that any uploading is happening, and there is no increase in gb of photos stored despite two overnights of possible uploading time. We have the optimize iPhone storage option selected, and there is plenty of room on the new 50gb plan for her 12 or so gb of iPhone photos... We do have a slower connection, but there remains no indication that there is any progress whatsoever. We sign into iCloud on our Mac, and the total of pictures on her account stopped uploading well back in June with only 732 pictures, while there are some 4000 or so on her phone awaiting upload.