I had the same problem this fixed it:
sudo apt-get install mtpfs
Once that's installed, plug in the phone to your computer. If nothing happens, on the phone go to Settings > Storage > Upper Right Corner (⋮) > USB Computer Connection > Media Device.
Settings > Search (type in "usb") > USB configuration ... If non existent make sure developer options have been enabled.
Open Settings> About> Software Information> More.
Then tap “Build number” seven times to enable Developer options. ...
Go back to Settings menu and now you'll be able to see “Developer options” there.
Tap it and turn on USB Debugging from the menu on the next screen.
Once they have been enable and the above package installed, also be sure to have the phone plugged in and then go back into developer options and update the USB configuration as shown in the picture below.