If you have problem with your database, change your password or delete and create it and try again.
Free hosting server might be abuse at time and it might not be available from time to time.
+ You have to create the database using mysql icon before you can use it
+ It might take a little time from the time you create until it is available, please make sure you check using PHPMyAdmimn first before you try to configure it with your application.
+ Your config should point to MySQL hostname with 'mysqlXX.000webhost.com' format.
+ 000webhost version of PHPMyAdmimn is connect using 'sqlXX.000webhost.com' format.
Please check Mysql icon in your cpanel for more connection detail
Note: Remote Mysql is not allowed on 000webhost free hosting,