Update: I worked it out. I have to have the Agent set to Personal Media Artists. Then I have to be in album view. I click the three dates on each album, then Match… Then I could see a little icon with 100 next to it… I clicked on it and the artwork loaded.
My server on my Nvidia Shield stopped working. I formatted the shield and made a new server. I added the music from the same directory, with the same files, with the option selected to find embedded album art. Most album art is missing. I checked some of the files in mp3tag and the album art is still there but plex isn’t finding it. All album covers showed before.
Does anybody know what I can try to get the embedded art to show? I have tried refreshing metadata, analysing and rescanning the library.