Why is the VPN switch sometimes missing from settings on my iPad?
Check for a VPN Profile
Turns out the missing VPN switch had nothing to do with which connection was used.  What seems to have happened is that all the VPN profiles were deleted.  When that happens, the VPN switch seems to disappear.  To check for or create a new VPN profile, go to settings-&gt;general-&gt;network-&gt;VPN:

Once you create a VPN profile, the VPN switch reappears in the root of the settings screen: