Users cannot sync Google Drive when SSL interception is enabled on ProxySG appliance.
The only solution is to bypass SSL Interception for these connections. This applies to both transparent and explicit connections.
This occurs because SSL certificate validation is done by the Google Drive application. Because the certificate used for SSL Interception is either self-signed or issued by a locally-signed CA, Google Drive certificate validation fails.
If there is an SSLV involved, you may need to ensure this device is set to cut through this traffic. If this solution does not resolve the issue, see if the SSLV SSL Connections are erroring.