Apologies, I know there have been a million variations of this question, but I haven't had any luck with any of the solutions I've seen.
My Plex integration configured manually via the app tile since it runs natively and not in docker. I have added 401 to the allowed network codes, so it shows as green when configured with my Plex token. For configuration, I am using the internal server address and port with a typical https prefix. I do also have the external address and port entered in the external address field.
My media server widget shows a red ring around the Plex logo in the lower right of the widget. Logs here: https://pastebin.com/BatBSHSE
A sleek, modern dashboard that puts all of your apps and services at your fingertips. Control everything in one convenient location. Seamlessly integrates with the apps you've added, providing you with valuable information.