This is a limitation of macvtap. You need to setup a bridge. There are few posts about that in this thread.
This could be your server or storage or how you are connecting. The consoles provided by the plugin are only meant to use for setup. You should use the native RDP server on Win 7 (which is EOL by the way).
I did it on the advice. Delete the interface in the GUI without clicking apply, added the BRIDGE, and all the other default settings(DHCP for the interface, etc.), then clicked apply and lost the connection. I had to physically go to the server and restore the network interface through omv-firstaid