openHab phone app and VPN

I have had openHAB phone app version 2.16.0 for years.

And I have OpenVPN set up on firewall.

In the past, all I did was fire up the VPN client on the phone (either on a public wifi or via 4G) and the openHAB app would connect to my OH server.

openHAB app still works just fine when I’m not using VPN on my home network.

But, now it won’t connect to the OH server when on VPN. I can ping the IP of the server, it is on the green interface of my firewall.
But the OH app can’t connect…

I don’t remember ever having to port forward on the VPN/firewall to get to the OH server.

Looking for ideas…and I did some searches here in the forum, but not much turned up.
I probably didn’t get creative enough with search terms.