If your device isn't recognized, verify that it's configured correctly. See the user manual for your device for more information.
Certain devices may be recognized only when used with a powered USB hub.
Here are the supported SD cards and image-transfer protocols:
Picture Transfer Protocol (PTP)
Mass Storage Device protocol
SDSC
SDHC
miniSD
microSD
MMC
SDXC
If your camera supports both PTP and Mass Storage Device modes, you may need to use both modes to import all media content. If some files don't import as expected using one mode, try switching to the other mode and importing again.
Some cameras may refer to PTP as Pictbridge or PTP/Pictbridge.
If you see a message that the "Attached volume appears to be invalid," make sure the SD card or digital media in the camera is correctly formatted.
(Apple Support)