Google Map show on the homepage but not other pages. Why?

Problem

My client has a Google map added to several pages of their website. The map on the homepage is working perfectly. Which confirms that API is connected correctly. But maps on the About page and Contact page don't show up.

There is the following error in the console:

In the Google documentation information about this error is as follows: 

Solution

After a short research I found out that if client restricted domain that can make call to map API all exact URLs where map is located should be added to the list of HTTP referrers. So adding a root domain is not sufficient. www.mysite.com/contact URL should be also added to the list.