Hi there frankakn_7,
This could be due to a number of factors but firstly, head to Settings > Mobile and under mobile data ensure that mobile data is enabled for "Files".
Alternatively, the following may help:
- Log out of iCloud from settings, then log back in
- Turn Aeroplane Mode on, wait for 30 then turn it off
- Restart your iPhone
Failing that I would suggest a call to Apple Support.
I hope that helps 🙂