I've had same problems with Moto 3rd Gen, and it just happened for the 3rd time in 3 months. I don't have a solution but thought I'd highlite my experience.
NOV 2015 Consumer Cellular supplied Moto 3rd Gen with Lollipop. I tried SanDisk 32G Class 10 and phone
wouldn't recognize that or any card. But that and other cards worked in a older HUAWEI. I read that Lollipop
had problems with SD cards. Decided to wait for Marshmellow release.
FEB 2016 I updated the Moto 3rd Gen with Marshmellow, and still had the problem. Saw some reviews
indicating Moto 3rd Gen had electrical connector problems with SD card slots so I asked Consumer Cellular
for replacement.
MAR 2016 Consumer Cellular replaced the phone with a new one and the SD card worked! I formated
SanDisk 32G Class 10 as internal and used for all photos and some apps.
After a rew weeks of everything working well, phone message SD card not working and should Forget. I did
not select forget several times, and SD card became unrecognizable. Eventually lost all data, and SD card is
totally unusable; Can't even format SD card on phone or PC.
JUN 21, 2016 Received new SanDisk 32G Class 10 from Amazon and installed and formated as Internal.
Moved all recent pictures and a few apps.
JULY 5 2016 Again, all of a sudden, message SD card not working and should Forget. I selected Forget, lost all
my pictures, but was able to reused the card a portable storage.
I'm beginning to believe that the problem is with Android Marshmellow, Consumer Cellular patches, or Moto
3rd Gen device. Also, I just read that the Instagram App can cause problems with SD cards. That app just
updated on my phone in the last 24 hours.
I'm planning to test a Moto 3rd Gen that was purchased directly from Amazon to see if I can start to bracket the
likely caueses.