No one was responding so I searched around and found another thread on this in case anyone is still having an issue.
Link to thread
https://forums.plex.tv/t/not-found-were-having-trouble-finding-this-page-it-might-have-been-deleted/711334
Suppose to Reset Defaults on the Plex Web Debug page under your server settings
https://app.plex.tv/desktop/#!/settings/web/debug
Seemed to work for the majority so good luck
