Moto G3 (android marshmallow) not detecting SD card anymore (solution?)
This worked for me:


Removed the SD card from the phone 
Plugged the SD card into a MicroSD to MicroUSB adapter 
Plugged the MicroUSB adapter into the MicroUSB plug on the phone 
Run ES File Explorer and in my case the SD Card was
named '0'. I was able to access the DCIM folder and upload all my
photos and videos


NOTE: ES File Explorer Ver 4.0.5.5 was used. When I upgraded it to the latest version so I could upload to Google Drive, it no longer could recognize the files, so I had to downgrade back to 4.0.5.5 and use Dropbox.