I’m also having a similar issue.
Server version: 1.21.4.4079
Operating system: Windows 10.0.19041.906
My issue is that when trying to launch Plex, it just pops up with a dialog box that says “ERROR” no further info given, just the single word.
Plex is not shown as running in task manager for me.
Since Plex won’t even start, I don’t have any logs to share (unless they’re stored in a different location than either of these) -
%LOCALAPPDATA%\Plex Media Server\Crash Reports
%LOCALAPPDATA%\CrashDumps
I’ve already tried rolling back windows updates, and rolling back the version of plex media server to previous versions which I knew were working.
I browsed around the forums and tried the .dll swap talked about in this thread, but no luck: MFPlat.DLL issues with Windows 10 Pro N - #2 by BobSnot
Super bummed cause I just got a Plex pass, and now the media server won’t work. 
