Use openwrt as vpn tunnel

Hello everyone,

I currently have a USG in use, Unfortunately I can't install a VPN on the USG because the model is outdated I would like to create a pia vpn tunnel to connect a few proxmox containers to the internet via vpn.

So I installed Openwrt with openvpn and pia vpn in a Proxmox LXC with this tutorial -> https://www.youtube.com/watch?v=3mPbrunpjpk
everything works.. until I change the network adapter of the lxc(sonarr) from vrmb0 to vrmb1. Then the web gui is no longer available via my windows machine.

Any idea how I can solve this?

Windows machine and the proxmox server is connected via unifi switches and USG.