SD card not recognised

I purchased the camera approx 3 months ago and have had a few problems of which I can live with a few. However I have two main problems and hoping for some help here. After running through the initial learning stages I arrive at the SD disk, I can manage a few photos with the studio but then it tells that I have no SD card? I have taken no more than 10 (max) photos. I have read the warning about formating the new disc and have done so, still informed that I have no SD card. Now I operate a late 2015 iMac, always updated, but after transfering the card to a reader the computer tells me that the disc cannot be read. Just in case I bought a new card from Amazon and the same results. My final conclusion is that Mac cannot read the card or I am making some serious errors, as I am sure there are many people here using Macs and cannot find the same problem mentioned. The videos of the camera and the studio are amazing and I am not giving up yet so any answers would be greatly appreciated.