When you go into the Manage Content section to the left you will see the folders listed. If one folder is grayed out, please click on the folder and look to the right for the file location, this will be in blue lettering. Please write the file location down.
As an example, if my Commercial Art Kits folder was gray on the left, I would select Commercial Art Kits and look to the right to see where the blue file location and then write it down. For example, the Commercial Art Kits typically are stored in C:\Users\Public\Documents.
Then you will want to right click on the grayed out folder and select 'Change Folder location or remove folder'. This will open up the next box where you would want to select option 4. This option will prompt a warning box for you, please click on Yes. *WARNING* If you remove this folder location from the library, the kits in this folder location will be removed from any categories into which you have placed them.
After you do this, you will need to right click on the Library option from the left side and select Add Folder to Library. This will allow you to browse to the location that you wrote down. In the example I provided I would browse to the C:\Users\Public\Documents and single click on Commercial Art Kits and select OK.
It may take a moment but your kits will be added back to the content manager without the question mark on them.