Can't write to 64 gig Micro SD card with Android 4.4 & Note 3 Phone

I have a Samsung Note 3 phone, Android 4.4.4 (updated to it a few months ago) and a Sandisk 64 gig micro sd card. I used to be able to transfer files (mp3 music and videos mainly) to the Sandisk card by dragging and dropping from the computer to the card (using windows explorer or just clicking on the card in “My Computer”  (still recognized on the computer) and dragging the files to wherever I wanted on the card. Now, and I’m not sure if this is just since the 4.4.4 Android update (although I think I was able to do it for a while), but now I can not transfer to the phone. Fortunately, I can still backup the card to my computer with a USB cale, but not the other way around. 

I just took the card out of the phone, plugged it directly into my computer port, and I can transfer to the card from the computer, but I don’t think I was even able to do that a couple of days ago when I tried. I tried so many things that I’ve lost track of what I’ve tried.

Could the Sandisk card have become “unstable” (works sometimes and not others)? Or is it something with the phone? I know with Android 4.4.4 it won’t let you transfer apps from internal memore to the card anymore, but I thought this didn’t effectr music mps file, etc.  transfer.

I spent an hour on the phone with AT&T support (my cell carrier) and the rep claimed they are not aware of a transfer file issue like this with my phone and operating system.

By the way, I am able to delete music files from my sd card when it’s in the phone, but not transfer to the card.

Int he meantime, I’ve ordered a new Sandisk 64 card and should have it in a couple of days, just in case the card hass gone bad.

If yuou’re still reading this, thanks for your interest, and any ideas would be appreciated!