Using OpenVPN (via server on my Synology NAS) with new Plusnet Hub 2 on Fibre broadband

[#1]

First post here - bear with me if I leave out needed information. I'm fairly computer-savvy, but a novice when it comes to VPN setup.

I just last week was connected with Plusnet full fibre and a Plusnet Hub 2.

I have an OpenVPN server on my Synology NAS, which seems to be working well.

I can connect to the OpenVPN server via my Plusnet router no worries - at least both my phone and the server can see the connection and say I'm connected.

Unfortunately, I can't access anything on the network or internet from my phone using the OpenVPN connection - I can't see the NAS, nor can I access any internet sites (even pinging 8.8.8.8 doesn't work) - even when using a Split-tunnel configuration.

There's clearly some sort of setting/firewall that I don't know about that's blocking outbound connections from the NAS

I've updated both my NAS firewall and my Plusnet Hub 2 firewall to forward the OpenVPN port - and as I say the connection is working fine. Plusnet Safeguard is OFF. 

Any suggestions? Are there other firewall settings I need to sort out? What could be blocking the outbound connections? Have I overlooked something obvious?

[#2 · Accepted solution]

Ok, more troubleshooting. It's not to do with Plusnet. I disabled my Synology NAS Firewall and that fixed the issue. So the changes I made to the synology NAS firewall this afternoon obviously caused the problem.