I had a problem with a 64 GB SDXC card yesterday. It’s capacity showed as “1 MB” on all devices and showed both “NO SD” and “SD ERR” in my GoPro Hero 3+ Black (v3.0.0). I tried formatting using a computer (Win 8) with diskpart.exe as well as other reformat tools. No luck. I then plugged it back into my GoPro and tried reformatting it on there (settings>erase>erase all/format). This seemed to fix the problem and it now recognized it as a 64GB card on my devices and functions normally.
That said, there seems to be no way to recover any data on the card. This needs to be addressed by SanDisk however I have not yet gone through the hassle of contacting them.
