Lost server after network reset

There is no active VPN on the PC or NAS, correct?
You used http, not https, and the NAS IP address? Ex: http://10.1.2.3:32400/web
And there is no response at all, not even the 503 maintenance message?

Try http://syno_ip_address:32400/identity.
You should see some XML. Do you see claimed="1" (or 0)?
This would confirm that Plex is running and in a claimed (or unclaimed) state.

Try rebooting the NAS, then try accessing Plex once the NAS is fully booted. Sometimes a reboot will clear out some cobwebs. Use an incognito/private browser window to bypass any ad blockers, cookie cutters, etc that might get in the way.

If you still cannot get into Plex, then time to look at the log files.

  1. Stop Plex
  2. In File Station, navigate to the Plex Data Folder, /PlexMediaServer/AppData/Plex Media Server
  3. Right click on the Logs directory and choose Compress to Logs.zip.
  4. Upload Logs.zip to the thread.