I’m going to tell you how I fixed the failed to start application error for a client recently, but first, a quick word about Joomla.
I don’t like Joomla and I never have. I always try to steer clients who are considering Joomla to WordPress or Drupal. Even Wix is a better option in my opinion. If you want to know more about my reasons for this, feel free to contact me.
This particular error, however, can’t necessarily be blamed on Joomla. It often has something to do with a misconfiguation in your configuration.php file, a problem with your PHP version, or with your database itself.
I encountered this failed to start appllication, error start the session error on a recent project. I immediately logged into phpMyAdmin and noticed my clients mysql database was 10 megabytes over the host’s limit!
I contacted the host to increase the maximum database size limit and suddenly the website came back to life! The issue was that because the database was oversized, Joomla could not write any information to it (including sessions).
This may not be the reason why your site is showing this error but it’s definitely worth checking out.
If you need some help debugging your Joomla issues, feel free to contact me here.