1. Go to the Google API Console.
2. Create or select a project.
3. Click Continue to enable the API and any related services.
4. On the Credentials page, get an API key.
Note: If you have an existing unrestricted API key, or a key with browser restrictions, you may use that key.
5. From the dialog displaying the API key, select Restrict key to set a browser restriction on the API key.
6. In the Key restriction section, select HTTP referrers (web sites), then follow the on-screen instructions to set referrers.
7. (Optional) Enable billing. See Usage Limits for more information.
If the problem persists, please share us the admin account of your site via private reply so we can investigate your case and help you out. Also, please point to specific page where we can see the problem. Any screenshots would be welcomed!