I enabled a Google Maps API, but I am encountering an error stating that this page can't load Google Maps correctly. The error message indicates that it's for development purposes only. Please provide guidance on how to rectify these errors.

In need of guidance to rectify errors encountered when trying to load Google Maps API. The error message states that it's for development purposes only.

Requirements:
- Knowledge and experience in working with Google Maps API
- Ability to troubleshoot and debug code
- Familiarity with clearing cache and cookies

Skills:
- Proficiency in JavaScript and HTML
- Experience with Google Maps API integration
- Strong problem-solving and debugging skills

Responsibilities:
- Analyze code to ensure correct entry of API key
- Verify the setup of necessary billing account for Google Maps API
- Guide in clearing cache and cookies to resolve the error

Note: The client has confirmed that the API key is correctly entered and the necessary billing account is set up.