A lot of 64 GB cards come pre-formatted as exFAT, which isn't compatible with many devices (I'm not sure if it's compatible at all with Android). If your card is formatted as exFAT, try reformatting it to FAT32. You can try doing so by inserting it into your computer, although when I tried doing this, I found that Windows 8 doesn't give the option to format in FAT32--only exFAT and NTFS. Typically, if you insert an incompatible SD into a phone, it should ask you if you want to format it, in which case it will do so in the appropriate format.