Unable to open configuration file "C:\Program Files\Google Apps Directory Sync\sync.xml", unexpected error while attempting to open it
Manually recreating my configuration by sifting through all 22 screenshots sounded tedious. Based on this error message, my first assumption is that the .xml file is referencing credentials or an authentication method that is now deprecated in GADS 4.0.3. I opened the .xml file in Notepad and immediately found the "oAuth2RefreshToken" that stores the encrypted credentials.
As always, good luck and happy scripting!