Plex control, playing, accounts

Probably an issue with your file naming or organization.
https://support.plex.tv/articles/naming-and-organizing-your-tv-show-files/

Plex assumes that remote access is working while it’s still checking the status. Therefore a green status indicator switching to red shortly after opening the page means it never worked to start with.

Usually deleting the entry from the list of authorized devices should do the trick.
https://app.plex.tv/desktop/#!/settings/devices/pms