Thanks for using Codebook and posting to the discussion forum, although I’m sorry to hear about the trouble with Google Drive sync.
From the description, it sounds like you could be using an outdated version of Codebook for macOS. Would you mind checking what version of Codebook for macOS you’re currently running? That can be found at Codebook menu > About Codebook.
The latest version of Codebook for macOS is 4.5.19 which includes a Google Drive permission change: Codebook for macOS 4.5.19 Released - Google Drive Permission Change
If you’re using anything less than that, would you please update to the latest (either in the link in the update post if you’re using the direct version, or via the Mac App Store if you’re using the App Store version).
If you are already using the latest version, could you let me know what the error message says when you attempt to start the sync? Thanks!