Missing traffic is never a problem of the scenery, there might be multiple causes for it:
- Your AI Traffic package is not made with native FSX models. In this case, AI will not appear on sceneries with custom runway textures UNLESS you turn OFF the "Airplane Cast Shadows on ground" option.
- Your AI models don't have airline codes applied, so they might park randomly, perhaps at remote areas you don't notice, since the scenery uses only airline codes rather than parking types, in order to get rid of default ground vehicles, so it requires all AI being flagged with atc_airline_codes in their aircraft.cfg file.