I have a tablet AOC Breeze model MW0712 with Android 4.1.1.
When I want to save an APN I do: Settings -> Mobile networks -> Access Point Names -> New APN
But after editing the APN settings, there are no button to save the changes.
The only proven way I have to save an APN is typing in the fields:
and leaving blank the MCC, MNC, Authentification Type and APN Type fields. With this way the APN is saved but doesn't work. If I edit the APN I've saved and I put the values for these fields, the APN disappears.
With Root Explorer I open the apns-conf.xml file (readonly) and I see full of different APNs, but APN selection screen (Settings -> Mobile networks -> Access Point Names) is empty.
I haven't rooted the tablet.