Apache 2 Not Working
If Apache did not restart successfully, you'll likely be able to gain more insight by reviewing your Apache error logs. By default, these logs are typically located in the following directories:
You can run the following command to view the most recent entries as the log grows (replace the path in this example with the location of your error log file):
sudo tail -f /var/log/apache2/error.log
This resource on Apache's website can help you review entries from your log files, and it also describes how to configure Apache's various logging capabilities.
Linode also maintains a fantastic guide on troubleshooting issues with Apache: