My MicroSD files appear on my phone but not on my computer.

[AC Question]

I'm using a 120GB SanDisk Micro SD card in my HTC One M9. I've never had any trouble with it before. However, now whenever I connect the phone to my computer, the Music folder comes up as being empty, save for one small folder. Oddly enough, my phone can still access all my songs. However, I want to be able to copy and paste music between my phone and my computer. How can I make the computer see that there are folders and files inside that Micro SD card folder?