I just got this Verizon S4 (SCH-1545), current build MK2 Android 4.3, less than a week ago, and I came from an HTC sensation. Firs tthing I did was put my sd card from the sensation into the S4 just so my photos and music and everything else would be right there. If I remember correctly, Play Music might have saw a few songs at first, but I didn't pay much attention to it. The SD card is an Adata 32 GB class 10. The S4 is now not detecting the Sd card at all. My HTC sensation is detecting it just fine, and my computer is also detecting it just fine via usb to sd card reader. Another strange thing is that using a usb OTG adapter, the SD card is still detected. Meaning I plug in a cable to the micro usb port on my phone which has a female usb 2.0 port, which I then plug the sd card reader into. The S4 detected the sd card then, but not when it is plugged directly into the SD card slot. Other people have suggested other SD cards, I used a SAMSUNG 16GB SD card that came with a Samsung Epic 4G I had from a while ago. This SD card was detected by my HTC Sensation, and my computer, and neither have been detected by my S4. To format both of these SD cards, I have been right clicking them in windows explorer and clicking format. I have tried formatting both SD cards in format exFat, FAT32, and NTFS, and nothing has worked. I have the phone rooted and SafeStrap is installed, booting to Safestrap recovery also doesn't detect either SD card. There are other things that I have tried that I probably forgot to mention, but those were the primary fixes that I found and nothing has worked so far. If anyone can give any suggestions or link me somewhere where my exact problem has been resolved, I would very much appreciate it.