Aperture 3.6 doesn't load photos from SD card.

Hi

For a while Aperture, which I have on an old iMac and a 2013 MBP, has not been importing correctly. When I insert an SD card into the slot in the MBP, it used to show up in the list of devices when I clicked on the import button, but that has stopped. It now just shows the main storage drive of the computer. Fortunately the SD card shows up in Finder, so I can still import using drag and drop. But that means I don't get the option for the files to get deleted after the import.

Does anyone know what might have happened? There are a fair number of parts on this stack.

TIA

Mark