Here’s something I discovered.
Before iOS 11, I had iCloud Photo Library set to only upload/download pictures while connected to WiFi.
After I upgraded to iOS 11, that setting magically changed back to Cellular data usage for photo updates.
I noticed that when I opened the photos app, I’d always get the spinning wheel and it would say “updating” but never get anywhere.
I changed the setting back to WiFi only, but the photos app STILL tries to “update” while on cellular, and I get the constant spinning wheel.
This may be different than what your experiencing, but I would definitely see what cellular data options you have enabled.