You used some ‘Uninstaller’ or ‘Registry Cleaner’ software, right? Don’t. They usually do more damage than good.
pms-shutdown.msi issue: PMS-SHUTDOWN.MSI Error / FIXED!
Server Settings unavailable: Make sure you didn’t switch to a “managed” user account.
If you are already on your main plex user: https://support.plex.tv/articles/204281528-why-am-i-locked-out-of-server-settings-and-how-do-i-get-in/
Read those instructions carefully.
Make sure you know how to switch to the ‘incognito’/‘privacy’ mode of your web browser.
