No Google Groups showing up after setting up Googlegroups Sync extension
I am on Wordpress, but I had the same problem. I saw the group, but could not see the field. The reason was that my connection to Google API was not properly setup.


If you use Google Apps, pay attention, that on the Google Dev Console you create the Keys with a user which is a Google Domain Admin.
You also need to enable the Advanced API for Admin SDK. Search in Googles Developer Console for the Admin SDK and click on enable API.


When that was done, it took me a couple of hours of searching/debugging, the dropdown to select the groups appeared. 

regards,
Alain