Do I have to rebuild the BOVPN tunnel if I replace a Sonicwall with a T40?
I have replicated the Sonicwall settings to the T40 but the BOVPN won't come up.
You shouldn't need to.
What do you see in Traffic Monitor related to this tunnel?
You can turn on diagnostic logging for IKE which may show something to help:
In WSM Policy Manager: Setup -> Logging -> Diagnostic Log Level -> VPN -> IKE
In the Web UI: System -> Diagnostic Log
Set the slider to Information or higher
Besides Diagnostic Logging, you have 2 other options when the session is trying to connect, and you should see something to help understand this.
1) Web UI -> System Status -> VPN Statistics, click the Debug button
2) in FSM -> Traffic Monitor -> right click -> Diagnostic Tasks -> VPN tab
And, you can always open a support incident on this to get help from a WG rep.