My note 3 will not mount on to my computer I used to plug it in, and it would show up and I could download the pictures and movies and such. Today, it will not mount. It is charging from the computer, but I can not download any of the stuff I've done. 

Running windows 7 on my computer.

I've turned it off and on again, it is not working.

I probably have added an app or two, I am not sure. It has been a while since I uploaded from this phone, but I plug it into the computer every night. Is it possible I accidentally hit a tick box and instructed it not to mount?
What operating system do you run on your computer? That sometimes happened to me when I used Windows. Have you tried using AirDroid, though? I use that now. It basically does remotely, what you would do with a USB. 

But that's just an alternative, I'll wait for your response to see if maybe I have a solution.