When Matomo (Piwik) displays an error message An error occurred: Cannot connect to the database this means that Matomo was not able to connect to your Mysql database.
To solve this problem you can:
- Contact your system administrators and ask them to verify that the Mysql server is up and running
- If your Mysql server is up and running, maybe the username or password used to connect has changed? To update the Mysql connection information, edit your configuration file
config/config.ini.phpto view and edit your connection details.