Thank you for the reply. I have actually removed / uninstalled PMS from the QNAP AppCenter since I wanted to rebuild everything but after re-installing using the latest version I got from plex.tv, it keep getting that message. Should there still be database upgrades from a fresh install?
As an additional information, PMS is now removed but when I go to the PMS web https://x.x.x.x:32400/. I still get that same maintenace message.
I stumbled across this article and it seems like I would need to remove data that may not have been removed during the uninstall. Does anyway know how I can do this in QNAP?