Fix WordPress Login Error

I'm seeking a skilled WordPress developer to resolve an issue with my login form. I'm receiving an error message that says "Username not found" when attempting to log in. I've already tried some troubleshooting steps, but nothing has worked.

Key Requirements:
- Access to FTP and WordPress dashboard
- Diagnose and fix the "Username not found" error
- Ensure login form is functional after repair
- Provide a brief report on the fix

Ideal Skills and Experience:
- Proficient in WordPress and FTP
- Experience with WordPress login issues
- Strong problem-solving skills
- Good communication skills