Join Date:Joined: Oct 2014
(Alright, after having been a long passive user of the xda forums I finally made an account to contribute).
Having read all the posts in this thread I wanted to add this:
I am also having trouble with 32GB Sandisk Ultra UHS-1 in my Moto G XT1039 running 4.4.4. I got the "Blank SD card or has unsupported filesystem" error twice. First time after I purchased the phone it worked fine for a week and then it gave me the error on the card (which works on the S3 btw). The I reformatted it but got the error again a couple of days later after rebooting the phone.
I was speaking to the Motorola support on the live chat and he asked me to check whether the card still wouldnt work if I popped out my sim. And, strangely, the sd card DID work when my sim card was not in the phone. Subsequently, I put the sim back in and the SD card works. (This is no solution though since Spotify wont recognize the downloaded files anymore - so I'll still have to download those GBs again...)
All in all, it does seem to be a hardware issue (esp since it does work when the SIM is not in the phone ???).
Now, the Motorola supported suggested I'd send my phone in, but I'm hesitant 'cause I can't do without the phone really.
So does anyone have had this issue with a class 6 sd card? If not I'll buy one of those and leave it at that.