Fix Database Connection Error

I need assistance to resolve an "Error establishing a database connection" issue that arose after migrating to a new server. I haven't yet checked the database credentials in the configuration file, so guidance on how to do this would be appreciated.

Key Requirements:
- Diagnose and fix the database connection error
- Verify and correct database credentials in the configuration file
- Ensure the database is accessible and functioning properly post-fix

Ideal Skills and Experience:
- Strong experience with database management and troubleshooting
- Familiarity with server migrations and potential pitfalls
- Ability to guide and instruct on checking and updating configuration files
- Experience with common databases such as MySQL, PostgreSQL, or SQLite

Your expertise will help restore the functionality of my database connection. Thank you!