I found port forwarding on the Hub 3 to be very temperamental. I tried it for a few days and gave up with it, it worked sort of, sometimes taking a few attempts setting ports etc. Soon it stopped forwarding but the settings were still there. Factory reset and try again and it still kept 'forgetting' to forward connections after a short time. Replaced it with my Billion and everything worked fine. Invest in a good third party modem/router.
Here is the solution that's worked for me. I too had this issue from my last router to this new one.
From the Plex server settings, turn OFF Remote access.
Reset your BT Hub.
Turn OFF the BT Hub firewall.
Turn ON Plex Remote access.
Check it's enabled and you can access it remotely.
Turn ON the BT Hub firewall and check again.
All works for me now.
Hope this helps.
My above solution DOES NOT WORK!
It worked for 3 days then it went back to being unable to be available remotely.
Really annoying. Oh well. Carry on research for the solution.
Unfortunately port forwarding on a lot of hubs is temperamental. The solution for stable forwarding of ports is to invest in a good third party router. Two servers here on third party router work fine, never any connection issues.
Hey Liam. thanks for this. Any recommendations on routers as I think after all the things I've tried this is going to be the only way?
Personally I use a DrayTek Vigor 130 modem with a FritzBox 3390 in router mode, (DSL disabled). TP-Link do a VDSL router costing around £30. The TD-W9970.
Others with more bells and whistles can cost substantially more.
You may want to take into consideration the information linked to here before deciding on what to purchase.
It didn't occur to me right away that you mentioned having an FTTP modem. So that widens the choice of routers available as it's the VDSL modem component that seems to be problematic if not passed the MCT (Modem Conformance Test - Sin498) and not applicable in your case.