SD Card Will not work on Imac

I cannot get the sd cards to work in my Imac. It formats it on the camera and then it doesn’t work They told me to download the app and I did, but the computer still won’t recognize it.

If the SD card does not work on your camera either your computer, please change another SD card and have one more try.
Please remember to cut off the power when you install it or get it out from the camera.