What is the meaning of the ggmap error message "HTTP 400 Bad Request" when it states that the request has been rejected by the server of Google Maps Platform due to an invalid API key?

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The "HTTP 400 Bad Request" error message in ggmap indicates that the request made to the Google Maps Platform server is invalid. In this specific case, the error message suggests that the API key provided is incorrect or invalid. Google Maps Platform requires a valid API key to access its services, and if the API key is invalid, the server cannot authenticate the request and will reject it. Therefore, it is important to ensure that the API key provided is accurate and valid to avoid this error message.