Can you use the VPN on the Orbi 850 Router behind AT&T BGW320-505 and IP Passthrough

I think the subject covers it.  I've read a few posts saying they did it, but many more asking how to with no answers.  Someone suggested setting it to TCP instead of UDP, but that didn't help for me.

Does anyone know if this is technically possible?  I've turned on the OpenVPN software on the Orbi router but when I try to connect from outside my house, the logs on the Orbi never show that the attempt makes it there.  I used to have Comcast instead of AT&T fiber and this worked perfectly (the cable modem was in bridge mode, so obviously a different set-up than the BGW's IP Passthrough).  I've turned off every single firewall feature on the BGW.

Has anyone ever gotten this to work?  

Thanks!

DB