Can't preview my project, error while connecting to database


The name of my project: websitechineriefest
It’s a private project.

When I click on the preview button (after runing the project), I stumble into this page.

In english this means: Error while connecting to database.

This shows in the console:

Starting Apache httpd, serving Started apache2

I check into my config.php file, the information to my MySQL are good.

Do you have any tips on how to properly connect cloud9 to my own MySQL?