Google have changed the way they handle Maps, so in order to have a working Map on your web site now the following is required:
1) Google account.
2) Debit ot Credit card to enable Billing with Google.
Once you have both, go to: https://console.cloud.google.com/billing and click on: Add billing account:
Fill in your data and complete the set up.
Finally, go to: https://console.cloud.google.com/apis/credentials
On the Credentials page, click Create credentials > API key.
The API key created dialog displays your newly created API key.
The new API key is listed on the Credentials page under API keys.
(Remember to restrict the API key before using it in production.)
Copy the key:
then go to the ProSite web site builder and add it to your Map:
And click on Apply at the bottom to save the change.