rroeleveld
Yea so if you read the requirements of osTicket the web server must be Apache, LiteSpeed, or IIS. NGINX can be supported but it requires you to add special configs to the NGINX configurations. You can review older posts to find a full working NGINX recipe. You can copy that and update it to fit your environment.
Other than that you can switch to an out of the box supported web server like Apache, LiteSpeed, or IIS.
Cheers.