hmmm, not understanding totally the Plex Home. let me explain the steps I did a bit more, might highlight where i went wrong and also raise/exclude options.
1 build plex server at my house, IP 192.168.1.61 and use my plex credentials, copy media over
2 take to friends house, get onto network, IP 192.168.1.20, switch on, still my credentials, it now just said searching for media server, should prob have stopped here and first fixed it... hindsight...
3 go onto plex web site on his laptop (another computer) and create plex account via www.plex.tv
4 go back to Raspberry pi, reboot, when it came back on we said log in as someone else and provided his new credentials, still just searching for PMS.
5. somewhere along here, looking to see if i can find a IP address in the the settings settings I saw pin, selected that and provided a pin,
6. after a reboot, with some trying around different things it now started asking for a pin to log in.
7 get home, used my credentials and previous 192.168.0.61, all working... so know it's something to do with either his credentials or IP.
8. created a vlan on my network quickly, 192.168.1.0 and assign 192.168.1.20 to the plex via MAC Bind.
9. rebooted and tried to log in as him (confirmed plex now has the 192.168.1.20 IP at OS, yes...) and back to same problems.
10. Complete rebuild Raspberry, as in format memory card, reinstalled Raspberrian, reinstall plex.
11. when it comes up, it already knows about his username and just goes through to the enter pin, that then leads to a screen where it spins it's wheels looking for PMS.
I've now gone and trying to totally delete the plex profile from plex web site.
basically starting over. I'm at work, I rebuild the Raspberry last night again before I went to bed and will re-install the Flex software when I get home.