Don’t panic if you get this error message while using Sonic WALL VPN.
Just follow the below steps ,
Go to Control Panel->Network Connections.
Right click on SonicWALL VPN Connection\ SonicWALL Virtual Adapter and click Enable.
Now you should be able to connect.
If you are still facing issue “The connection ‘IP’ requires the use of the SonicWALL Virtual Adapter, however this adapter can not be found. It may have been disabled or uninstalled. Please check your network configuration.” issue, then please consider reaching to SonicWALL support forum.