Hi @Jackhol ,

Since its OnSubmit getXMLAnswer() wouldn't work here since its Async form will be submitted before response received from the script include

use getXMLWait()  instead (FYI: this wouldn't work if use this in Service portal)

ga.getXMLWait();

answer = ga.getAnswer();

if(

**********
unction onSubmit() {
    var assGroup = g_form.getValue('assignment_group');
    if (assGroup == 'a60fe98cdb27d85006d43ce3399619d7') {

        var ga = new GlideAjax('check_open_inc');
        ga.addParam('sysparm_name', 'checkAttach');
        ga.addParam('sysparm_ticket', g_form.getUniqueValue()); //Sending Ticket sys_id as parameter.
        ga.getXMLWait(); 
answer = ga.getAnswer();
        if (answer == 0) {
            var conf = confirm("You have not added an Attachment to this ticket, click Cancel to add an attachment, click Ok to continue");
            return conf;
        }
   
    }