The plug-ins are network aware and will search the network to see if the serial key is in use on another computer on the network. If you have multiple Macs running the plug-ins, check the serial key on each to see the keys that are being used. They can be found here: InDesign > About Plug-ins > Cognitive > AdImport/Fido/Split & Folio. The plug-in splash screen shows the serial key in the upper right corner.