[Moderator note: Topic title de-capped. Please do not shout at us.]
I have an error message appears:
Username and / or password defined in wp-config.php file is incorrect or that you can not connect to the server at localhost. It's also possible that the server is not currently available.
Make sure that the user name and password are correct, and they were entered without error in the configuration file.
Make sure the database server address is correct.
Make sure that the server is still active and available.
If you are not a technical person, you may want to contact Support to your hosting provider. Alternatively, you can contact a group discussion of WordPress.