This version (48.0.5.0) of Google Drive is outdated. Please download the latest version to continue.

Google Drive on Desktop for macOS was prompting me this message and then quitting, over and over. I ended up moving the app to the trash, reinstalling, and signing in again to get it working. Strangely, the version I downloaded ended up being 47.0.19.0 (which is older than v48) and the Google Drive for desktop release notes only mentions v47 released in April. Weird.

I hope this helps someone else in the same situation.