Mobile data not turning off for some apps iOS 8.4.1 I am unable to turn off mobile data for some apps.  Facebook, Cotap, Youtube and some others.  Yet some of the apps I can turn mobile data off for e.g App Store.

I recently upgraded to 8.4.1 on my iPhone 4s.

Any one have any ideas?
There's a bug which occurs sometimes where the CellularData.db is corrupted/malformed and iOS can't write the preferences to it.

You can fix this by deleting the file, located in /var/wireless/Library/Databases/CellularUsage.db.

Source: Fix cellular data app preferences not being saved on iOS 7