A Microsoft file hosting and synchronization service.
I tried all the normal stuff... uninstalling, reinstalling, signing out, signing in, toggling upload off and on -- all the seemingly "logical" troubleshooting. None of it helped.
This is what worked for me:
Try this counterintuitive fix…
- On your iPhone open up the OneDrive app
- Open OneDrive Settings -- click on your profile image in the upper left corner
- Under the category "Files and Photos", select "Camera Upload."
- Under the "Options" heading, make sure the "Download Using Cellular Data" option is toggled in the "ON" position.
It instantly solved my auto-upload problem. I hope it works for you.
iPhone 12, iOS 14.5.1