Have you checked to see if the checkmark is ticked to make it visible in browse mode? It is just to the left of the folders and layout names.
The number 50 rang a bell so I searched the Known Bugs List and there is a known bug once you get more than 50 folders:
For More Information see: 51 Layout Pop-Up Menu Folder limit…
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip