Connection issue: Hamachi VPN cannot see vehicle using remote access...

I am trying to have some software adjusted remotely on my car (BMW). The service provider uses a windows-based app to access the car's systems. The service provider is remote, and I we are having difficulty with the connection. I am on a M1 Max Mac running Monterey.

Within a windows 11 VM, i start an AnyDesk session, which seems to work. Service provider is connecting to my Windows VM using my wifi/router.
From there, he starts a LogMeIn Hamachi session on the Windows WM and is connecting to the car using a special cable which is OBD on one side, Ethernet on the other and connected to the Mac via a USB-C ethernet dongle.

At the next stage, he is trying to set up a VPN tunnel over Hamachi to access the car systems and can't. I have not changed any configuration in Parallels but did go through the KB steps to change Network Type to 2 in a config.ini file. I can't test this because I need my service provider but don't want to waste his time if that is not the issue. What should I be doing. here is the basic chain:

Service provider Windows-->AnyDesk Session on Windows VM using WiFi-->Hamachi-->Mac Ethernet Port-->On-board diagonstic cable-->car.

Not sure if this is a Hamachi issue or a port forwarding issue or a network settings or some combination. Specific suggestions appreciated.