Access Not Configured. YouTube Data API has not been used in project 608941808256

We had the same issue. We resolved it by starting from scratch and creating a brand new API project. For some reason the existing API project didn't work. Steps to check if you have this issue:

• Create a new project in the API console (click the project dropdown at the top of the window, and choose "New project").
• Enable the APIs required (e.g. YouTube Data).
• Go to credentials->Domain verification and enter your domain.
• Fill in the OAuth consent screen, and make the "application name" the same as your project name. Also choose the scopes you will be using, add your domain, save it, and submit for verification.
• Create credentials of type "OAuth2 client key->Web application" and enter the correct callback uri.
• Wait a few hours.

You should now be able to test in the APIs explorer (enter your own client key).

I had the same problem here.Besides enabling the Google+ API and the Contacts API I have also to create a new OAuth Client Key for Web applications.

When you create it you'll see that the client id will start with the Project Id that you have on the error message.

In summary you'll have to do as follow:

1. Create an OAuth Client Key with type web application
2. And the Client Id to you API

Then you should be able to authenticate.

Hope I could help.

I Solved this problem by creating a new project and then creating new credentials