I had to reboot my router, with the expected result that all of my local IP addresses have been scrambled and Plex stopped working. Fair enough.
I stopped it on the Diskstation, rebooted the NAS, but I can't restart Plex - I get the error saying that it "Failed to run the package service". I deleted the .pid file and the preferences and rebooted the NAS again, but still no joy.
I checked for updates, but I'm running 1.7.3.3937 and the version available for download is 1.5.7.4016 so the Package Centre won't let me downgrade to it.
Can anyone suggest a solution? I'm running Synology DSM 6.1.2-15132.