Request for Assistance with Website Login Issues

I am encountering an issue with the login functionality on my website https://apkpure.es/aplicaciones/descargar-tubemate-apk/. Users are receiving an error message that says: "Login Error: Incorrect username or password." This problem has been affecting users since [mention when the issue started] and is preventing them from accessing their accounts. Could you please assist in diagnosing and resolving this login issue to ensure users can access their accounts without trouble?