Aircraft in Content Manager but not Hangar/Aircraft Select

I have been working on converting a FSX Mini Max for MSFS2020 and wanted to test it. But when I added it to my community folder (directly, although I do use AddonsLinker for others), it isn’t recognized by flight simulator.
It does appear in the content manager, but the info says simply “Loading” and it is not present in the hangar or aircraft select in the world map.
Aircraft select (should be between the VL-3 and Cap10)

Content Manger

Info dialog

I have a similar problem with the Top Rudder microlight. Except it doesn’t appear at all. I can find the folder in my install folder, but the game doesn’t see it.

There are many reasons for this to occur, starting with improperly constructed manifest files, improperly constructed layout.json files, missing files that are necessary to define the aircraft, and on and on. It’s impossible to diagnose your problem based on the information given.