A Microsoft file hosting and synchronization service.
Are you keeping the OneDrive app open on screen during sync?
Keep OneDrive open, connect to Wi Fi and power, and do not switch apps since iPad pauses sync in the background. In OneDrive, go to Me, Settings, turn Camera Upload off then on if it shows. Then go to iPad Settings, OneDrive, turn off Background App Refresh, restart the iPad, open OneDrive, and test upload using Add, Upload with one photo.