Always-On VPN option does not list my PPTP VPN I have successfully connected to a PPTP VPN on Android. It is configured simply with an IP address, and no MPPE encrpytion. However, it does not show up under the Always-On option.

I am running Android 4.3 on a Nexus 4.
I was having this issue too. Apparently Google doesn't deem PPTP secure enough, so they disable it from the "Always On" menu.