Linking to User -> Tor -> VPN -> Internet - 4.1 broken?
I had the same problem with a VPN over Tor tunnel. There has been a bug, in which ARP rquests in direction to the VPN gateway have not been proxied properly by Qubes virtual network - see the github issue in above link. Workaround in above post as well.
Qubes developers have closed the issue, so I am wondering if this bug still exists?
(I yet need to setup a VPN qube again)
Also note, if you are using VPN over Tor, tasket/Qubes-vpn-support might harm anonymity because of IP forwarding being used - see linked Whonix maintainer’s statement.