AWS Lishtsail Wordpress troubleshoot

Hello, I'm looking for some help in fixing an issue I'm having with my AWS Lightsail Wordpress website. When the website is loaded, I'm seeing an error message that reads 'Error establishing a database connection.' I believe this is the problem I'm having, and I'm looking for an experienced and knowledgeable troubleshooter to help me resolve this as soon as possible. Your proposed solution must include advice on how to prevent similar issues in the future. If selected, I'll need you to work quickly to identify the root cause and have confidence in your ability to resolve the issue. Any questions about the project or other details will be answered promptly. Thanks for your interest.