As per following email from Google. 'Google+ Sign-In' is being retried shortly. It needs replacing with 'Google Sign-in'. Extension needs updating very soon. See: https://developers.google.com/identity/

Hello Google+ Developer,

We’re writing to let you know that as part of the sunset of the consumer version of Google+, we will be shutting down our Google+ APIs on March 7, 2019. As part of these changes, Google+ Sign-in has been fully deprecated and will also be shut down on March 7, 2019.

What do I need to know?
On March 7, 2019, all Google+ APIs and Google+ Sign-in will be shut down completely. This will be a progressive shutdown beginning in late January, with calls to these APIs starting to intermittently fail as early as January 28, 2019.

What do I need to do?
Please update your projects listed below by March 7, 2019 and ensure they are no longer using Google+ APIs. The data below shows which Google+ API methods your projects have recently called. [removed]

Note: If you see calls to people.get, these can be the result of using the Google+ Sign-In feature in your application, which is now fully deprecated and is being shut down. Developers should migrate from the Google+ Sign-In feature to the more comprehensive Google Sign-in authentication system.

Google+ integrations for web or mobile apps are also being shut down. Please see this additional notice.

Thanks for being a valued Google+ Developer.

Sincerely,

The Google+ API team