Make sure you update the firmware on the actual reader itself. I had this happen to me also while in the field. I tried a different SD card and it worked. I deleted all the pictures off the SD card that didn't work, reformatted it in the field, and voila, it worked again. Try that out. If that doesn't work, I have 3 Stealth cam SD readers I won't use. PM me your address and I'll send you one.
I currently have an iPhone 6s using the stealth cam reader and iBrary. My cards never read unless I take the darned stick out and stick it back in again.