Thank you.
I did look at the information previously and at first glance I don’t think these are the problem, but I will look more closely when I am able and go through each one.
Sorry I didn’t ignore the information you provided previously, I just wasn’t/am not currently able to check these.
I think what is confusing me about this is that if I can use the Android phone to access and play media using a browser on the phone, then the server and network are setup and working correctly (locally).
Therefore there is no reason the Android App, on the same phone, shouldn’t be working (locally) too… I mean if it’s a problem with the network configuration, then the web player also wouldn’t be working using a browser on the phone, right?
Or have I misunderstood something?
I understand if Plex believes it’s on a different network then it goes into remote mode, but then the web player also wouldn’t work would it?
and that narrows the problem down to the Android App itself, not the network setup.
(All ports are open, there are no additional routers/NAT interfering, it’s in the same subnet/IP range, etc).
Sorry if I’ve not been very clear.
When using the web browser on a different device on the network it says it’s playing “direct” and not “remote”.
I guess if I hadn’t tried the web browser and seen it working then I would immediately be thinking it was a problem with the network config. Or if using the browser it said it was playing “remote” that would indicate a network problem too.
I don’t know 
I will have another look at it tonight/tomorrow to see if I’ve missed something and go through the info you provided like a checklist to rule each one out hoping I find the problem.
Thank you 