Net Use hang with OpenVPN & Win11

I am trying to use a VNP connection between Windows (the client) and an OpenVPN server on a NAS. This works fine on Win10 but has problems on Win11. In both cases the computer gets assigned an IP address 10.10.0.nn; the VPN server gives itself 10.10.0.1. On Win10 when I issue (with the appropriate password and userid) it works. On Win11 it hangs for a long time and finally says
System error 67 has occurred.
The network name cannot be found.
That "network name" doesn't make much sense since the network name is this case is 10.10.0.1. A ping of 10.10.0.1 works so I know connectivity isn't the problem.

As a test I defined a L2TP/IPSec server on the NAS and client on the PC. That connection was made (10.2.0.nn) and Net Use worked fine. That sort of points the finger at OpenVPN ... except that it works fine on my Win10 laptop.

Anyone have any idea what's going on and/or how I debug this?

Update:
I should have included some additional information. I have Bitdefender running on my Win11 computers and Windows Defender on the Win10 laptop. I suppose BD could be interfering with Net Use but it logged not action taken ... and it usually loudly brags about how well it's protecting whenever it blocks something.

I'm running the OpenVPN 2.5.7 client on all computers - both Win10 and Win11. I have no idea what level server is running on the NAS.

The Win11 computers are running Pro 22H2 at various maintenance levels - all within the last month's maintenance. I don't have the Win10 laptop up at the moment so can't check its level

Update #2:
The NAS in question is on my LAN. To test the VPN I'm going out into the internet, back in through my router, and to the OpenVPN server on my NAS. (Actually the DNS lookup goes out into the internet. The actual connection from client to server just goes to my router and back onto my LAN.) That means I can access the NAS either by the VPN-provided 10.10.0.1 or by the devices "real" local IP address. Net Use works fine using the real local IP address; it's only the OpenVPN-provided address that causes it problems. And I just tried accessing the SSH server on the NAS via 10.10.0.1. That worked fine. Just Net Use on my Win11 computers has problems.