Error 792 - The L2TP Connection Attempt failed because security negotiation timed out.
Causes: 1. This behavior can occur because you have a preshared key that is configured on the client, but the key is not configured on the Routing and Remote Access Service server.
2. VPN server is not a valid machine certificate or is missing.
3. The IPSec Policy Agent service is stopped and started without stopping and starting the Routing and Remote Access service on the remote computer.
4.The IPSec Policy Agent service is not running when you start the Routing and Remote Access service.
5. The ISA Server computer is configured to block IP fragments.