Help with port forwarding

[#1]

Hi, Cam having great difficulty setting up port forwarding to run a Plex server from within my network. Plex uses port 32400 on the server machine and I have tried many options to pass requests through using fixed port on an external statIc Plusnet IP address to a local static IP address on the Plex server, swell as using DNLA, but to no avail.

My router is: Plusnet Hub One | Software version 4.7.5.1.83.8.237.2.2 | Last updated 14/11/17

Serial number: +081441+NQ73401742

I run the Plex server on Mac OS 10.12.6 (Sierra)

For this example I'm using external port 45633 forward to 32400 on the local machine. However, when I check the external port I find it is closed. See attached images. I've been at this now for many days/weeks and have unable to resolve the issue. I have also tried reseting the modem back to factory conditions but this has shown no benefit. I'm sure it must be me being a bit stupid. Any help appreciated.

Also, since reseting the modem responses from the modem and internet have slowed, even though download/upload speeds have remained the same.

Local port is openShowing port mapping external to serverShowing port mapping definitionShowing external port is closedShowingPlex not able to connect

[#2]

Unbelievable!!!!! I've been trying for weeks to sort this out. I desperation I just restarted the modem and now seems to work OK. I've done nothing more than I have done a number of times earlier. Bizarre. I may comeback to this thread again, but at the moment everything seems OK.

Is there particular sequences hat have to be used when adding port forwarding. i.e. reboot modem after certain steps, etc. As this is the only idea I have for answering the behaviour I have seen.