To test Login with Google the gmail address must have a Google + account created too.
Enable this option from theme options – Social and Contact -> Social Login as displayed in below screenshot.
Google Login requires you create an APP.
Follow these steps:
Login with your google account at https://console.developers.google.com
A. CREATE A PROJECT
Go to credentials credentials. Then to Oauth consent screen:
Type the name and optional homepage url. Save.
Next create the credentials:
C. CREATE CLIENT ID
Select to create oauth ID
Select web name, add site url, and add redirect URI (which must be the My Profile Page URL)
Click create. Close when done. You still have to create the part 2 of the API and you can copy all credentials after that.
D. CREATE BROWSER KEY
Go to credentials and create API Key
Type name and referrer url and click create
E. GO TO Library -> select Social
Enable Google+ API library
F. COPY DETAILS TO THEME OPTIONS – SOCIAL & CONTACT
Click on the name to get CLIENT ID and CLIENT SECRET
Copy the API key as well
Copy this in theme options – social and contact.