We are using the SH version, and currently trying to get gmail to connect. We have tried a lot of things and so far have come up empty.

We have the gmail plugin installed from marketplace, it shows up on the sidebar. We have turned on the mail integration in the database. When we click and email in gmail, and then try to login to the database through the plugin, it pops up the google allow access request. We click allow...and then just get a very generic less than helpful error message that indicates its a google error.
Big Odoo logo, under that it says "Odoo did not return successfully"

In the upper left of that same window it says "This application was created by another user, not Google"