As a result of macOS security settings and automatic updates you may see the following

Don't work - Its an easy fix (but not obvious or straight forward) so we'll guide you through it.  Open system preferences (Apple Menu > System Preferences) then > Security and Privacy > General Tab click on the allow button as pictured.  Note if when you open system preferences it jumps to a software update that means you have an update pending - hit the back button to get to the list of all system preferences categories or use the search bar in the top right corner to get to Security & Privacy

Once you've hit allow you'll want to quit and relaunch Google Drive File Stream - if you're not sure how to do that - then restart your computer and you'll be all set.