Why does InDesign ask for a serial key for my AdImport/Fido/Split & Folio plug-in every time I launch the application? -

Why does InDesign ask for a serial key for my AdImport/Fido/Split & Folio plug-in every time I launch the application?

This is a user access privilege issue. The user needs to have READ:WRITE access to the InDesign folder. Access to contents of the InDesign folder on newer macOS version do not default to full privileges, so the serial key for the plug-in is not getting stored.