SOLVED —I had the same issue yesterday. I was using the Sandisk 32gb class 10.
When I kicked off formatting from the camera/app, it got stuck and after that the camera stopped recognizing the sd card. I tried formatting fat32 using a Mac and a windows pc but it didn’t help.
finally, i downloaded the formatting utility from the Sandisk site and formatted the sd card using their utility which did the trick. The key difference in formatting via pc/mac is that the sd card shows 29.5gb available while the out-of-the-box the sd card is 29.7gb free space. Formatting using the sandisk utility gives back the 29.7gb which the Camera is able to detect. hope this helps.