If the Google Drive folder gets moved from its default location (username folder), the app will break and not sync. Deleting the app from Applications alone does not work because there are additional setting/plist files that need to be cleaned up. Instead, try the following steps:
1) Copy folder from wherever it is to the username folder, and ensure it is named "Google Drive". (Or create a folder if it was deleted.)
2) In the app, Disconnect the logged-in account
3) Log back in.
The app should re-sync using the Google Drive folder you moved. To test, create a test file or folder in the old Google Drive folder that was in the incorrect location. It should NOT appear on Google Drive online following a sync.