USB connection to MOTO E2 not working on Ubuntu 18.04
USB file transfer (MTP) more difficult Android > 6.0
If your Android is version 6 or higher setting up USB file transfer (MTP) is more difficult than before. First you need to enable developer options. Then you need to select MTP each time the phone is connected: How To Set The Default USB Connection Type In Android 6.0
Here is a screen shot from the link:
