When I open Accessory Kits Manager some or all of the accessory kits contain no parts (no parts listed in the bottom pane).
Accessory kits listed in the top pane of Accessory Kits Manager are part numbers in the active parts database that have a Part_Type value of ACK.
The Assigned Kit Parts pane reads from the SL_AccessoryKit table in the project database. This problem can be encountered when switching to a different project database or a different parts database.
The ideal solution is to restore the accessory kits from a previously created backup by using Import Kits button on Accessory Kits Manager. This adds the part numbers to the active parts database and the SL_AccessoryKit table in the project database.
Otherwise, if the accessory kits were created while connected to a different project database and that database is still available, the data can be transferred to the active project database using tools such as the Import and Export Data tool that is included with recent versions of SQL Server.