Some of the users of my VPN (with Network Extension) upgraded their OS to macOS Sierra.
For most of them, the app (still) works well, but for few - the app isn't working - they press the connect button, and nothing happens (probably startTunnel isn't being called). The only log I see from them is something about "plug-in failed".
I don't know if this is related, but for those with the problem - their initial OS was Yosemite (while for the other people, who hasn't had any problem, the initial OS was El Capitan).
The errors:
NESMVPNSession: Received a start command
NESMVPNSession: status changed to connecting
Subsystem: com.apple.networkextension
Failed to find the VPN app for plugin type
Subsystem: com.apple.networkextension
Failed to find the primary plugin
NESMVPNSession: status changed to disconnecting