Piwik error, CONFIGURATION FILE NOT FOUND

Hi,
I cannot enter in my piwik statistics and the message is:

CONFIGURATION FILE NOT FOUND
You can install piwik now
If u just intalled piwik before, in your database there are old installation table, dont worry, u can utilize and safe the existing data.

It happens from 3 days ago and I did nothing.

What can I do to solve and enter in my piwik?

thanks

Check if the database is running and config/config.ini.php exists.