SoapUI oauth2 token retrieval failure

I'm using SoapUI 5.5.0 and want to use the gmail api. The problem is that, when I setup the authorisation (type OAuth 2.0) and click on "Get Access Token", the embedded browser pops up with an error message "The page could not be loaded".

The Client id, Client secret, Authorization URI, Access Token URI, Redirect URI and Scope are correct, because I reverted to an older version of SoapUI (5.2.1) and was able to get the access token.

Any help to solve this would be highly appreciated.