Unable to find ‘full-path’ to my 404.php file

I just made it a full URL Path so https://example.com/404.php and that works great….kinda obvious – and I wonder if that is ‘not the WordPress way’

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)