PBXact VPN Client Undefined

I have an external S505 Extension that was successfully connecting to the pbxact using a vpn client and it suddenly became unreachable. In an effort to get it working I deleted the extension from the EPM and then re-created its entry. When I come to choose the vpn client from the drop down within the EPM/Edit extension I have only options of “none” or “undefined”. I have checked that the vpn client is listed within system admin/vpn server and it does.

If “none” as the vpn client is chosen, the phone connects, gets the background image/config etc and is reachable.
If “undefined” as the vpn client is chosen, the phone boots, the line keys have red lines through them , the display shows “vpn activated” , but no background/config etc is downloaded. The phone is also unreachable.

Any thoughts/clues?