So that suggests to me that this isn’t actually an issue with osTicket Awesome, but rather something amiss with your installation / web server.
500 Internal Server Error is very generic. The only way to get more information is to look at the Apache logs for clues. Look for entries that were recorded at the time you tried to create the ticket.
But often the cause is wrong permissions.
Please refer to the 500 Internal Server Error and What file and folder permissions do I need? sections on the Troubleshooting page.