Google Maps: The map is greyed out with a message stating "This page can't load Google Maps correctly"

This message means that there is something not set properly. In most case, it will be one of the following:

• the API Key is not correct: you can check your API Key for a project in your Google Map Console : https://console.cloud.google.com/google/maps-apis/overview
• you have not enabled Billing for this Google Maps project: https://cloud.google.com/billing/docs/how-to/modify-project
• you have set restriction for the use of this API Key for this project but the url where the error occurs is not part of the authorized URLs : https://developers.google.com/maps/documentation/javascript/get-api-key#key-restriction

On the page where the Google Maps error occurs, you can check the Developer Console (F12, Ctrl+Maj+I, ...). You will see the Google Map error and it will link you to the exact description of the problem and give you tips to solve it.