Getting Error 403: Access Not Configured. Please use Google Developers Console to activate the API for your project

You must enable a couple of API (in new google console) for things to work as expected.

Go to https://console.developers.google.com and make sure under "APIs" that you have following APIs enabled:

1. "Contacts API"
2. "Google+ API"

Try setting the "Referers" to "Any referer allowed" for your project (just leave the field empty) in the Google Developers Console if it is not already like that.

To do this, go to your Google Developers Console and open API & Auth / Credentials and click "Edit allowed referers" empty the input field.

I faced the same issue. While I am not sure of the reason and logic behind this, but the following steps worked -

1) I left the referers field blank (Any referer allowed). However, this alone did not work. 2) I regenerated the browser key. That did the trick.

Hope this helps.