Fix: Application Instantiation Error: Could not connect to MySQL.
You may receive the following error quickly (re-rendering the page it disappears) if trying to browse a Joomla 3 based web site.
Error displaying the error page: Application Instantiation Error: Could not connect to MySQL.
The error is related to not being able to connect to the MySQL site database. This can be the result of incorrect settings set on the database or a modification in the configuration.php pointing to your MySQL database file for the site.
All else, if the error suddenly appeared but not again after reloading the page, it may have been due to a brief loss of network connectivity with the MySQL database and the website as well.