AJAX requests such as this get routed by the AJAX UrlMatcher (
include/class.dispatcher.php). There are no subdirectories for AJAX calls. For example,
/scp/ajax.php and that file uses the patch after it to match and direct to the appropriate PHP methods.
Your issue is likely permissions on the temp directory. But you'll have to check your logs (general server logs, webserver error logs, PHP error logs, MySQL/MariaDB error logs, osTicket System Logs, Browser Console logs, etc.) for any related errors to be sure.