I think i'm fully back up and running. Here's a rundown of my adventure.
I've reset my password
Opened /appdata/plex/Library/Application Support/Plex Media Server/Preferences.xml
Made a backup
Removed the values from PlexOnlineHome, PlexOnlineMail, PlexOnlineToken, PlexOnlineUsername from xml file and saved.
Stopped the container
Added a new variable with a key of "PLEX_CLAIM" to container
Opened https://www.plex.tv/claim/
Copied the claim code into the value for the docker variable
Restarted the plex docker
It populates the Preferences.xml file with new data
At this stage I can access the web ui from direct IP. Trying to reach it from plex.tv, apps or custom domain wouldn't work
I went to settings, remote access and disabled it, enabled it, restarted docker again and now finally it's started working again.