Phone not showing as USB Connected
There are reports that the update to 8.1 has disabled USB storage functionality but there is a fix on the way (time table unknown). The only work around right now is to disable your lock screen, reboot, then you can connect it. This worked for me but it will stop working again as soon as you re-enable your lock screen (which obviously everyone should).

Sorry, but long story short, the update broke it and you'll have to wait for a fix.

A Motorola agent confirmed the issue on the official Lenovo forum