Locked out again... it's Plex

I have looked into my router’s software and can’t see that port 32400 is open anywhere.

I have a TP-Link Archer AX50 router and the software is the same as in this rather useful video:

I can see my NAS listed in the DHCP table but the Virtual servers page has no open port for 32400.

I presume that if I use the same process and put 32400 in the ‘Internal Port’ box and set the Protocol to ‘TCP’, that should work?

This article was helpful:

Again, any help appreciated.

I still don’t know why the Plex update suddenly stopped working. I’ve tested the port on the browser with the firewall off and even then, it doesn’t work.