Hello and welcome to Android Forums!
You may need to change how the phone is connecting to the computer. Without knowing what device you have, it is a little difficult to try and answer you.
If you go to "Settings", then "Storage" and select the 3 dots in the top right hand corner, you should be able to select "USB Computer Connection". I get 2 options with my Nexus 4 - "Media Device (MTP)" and "Camera (PTP)". Media Device allows me to transfer different things to my phone (like a USB device), whereas Camera shows my phone as a camera on my computer.
Hopefully, this should help you out - if not, post back!