Doesn’t look missing to me: https://watch.plex.tv/show/sealab-2021
https://watch.plex.tv/show/sealab-2020
It seems to me that the files of Sealab 2021 and Sealab 2020 are getting conflated in your library.
Try adding their respective release year to the folder names.
Sealab 2021 (2000)
Sealab 2020 (1972)
Then perform the old Plex dance with both Shows.
Don’t forget to check the “Collections” tab of your library. Seemingly missing shows/movies might be simply lurking inside a collection.
