I tried this with my Verizon Razr M, Android version 4.1.1. After I install the card, the Mount SD Card command is available, but after I choose it, I get a message that says Blank SD Card and the Unmount and Erase (Format) commands aren't available. I've tried with two phones and two cards, which makes it less likely that the results are due to a defective card.
Have the people who have succeeded had phones that were unlocked or rooted or are there some other steps needed to make the 64 gb MicroSDXC work? I've read suggestions to reformat the card from a PC to FAT, but others that say the card should only be formatted using the phone. Thanks.