I tried running the node under a different port and it did work... I did receive a couple of incoming connections... but over about 24 hours I never had more then 10 connections at once as far as I noticed.
When running the node NOT through VPN I was getting a lot more.
I'm currently trying a hidden service through tor as a full node to see if it is any better.
I doubt that a hidden service through Tor will be any better.
If you can run Bitcoin Core without a VPN, why are you using a VPN?