My idol 3 cell will not recognize the SD card.
Glad you were able to fix it although it sucks that you have to do everything again. Well, at least the SD card slot is still working.
I did try another SD card and no help so had to factory reset, it worked but painful to reload everything.
Try the SD card with other phones. If it works, there might be problem on your SD card slot. Otherwise, you need to buy another SD card.