It is because, the validator by default ignores hidden elements.
So when you use an accordion the input fields are hidden so they are not validated
$("#form_master").validate({
ignore: [],
rules: {
categorie: "required"
},
errorPlacement: function (error, element) {
if (element.is(":radio")) error.appendTo(element.parent().next().next());
}
});
Demo: Fiddle
Note: You may have to highlight the accordion tags with error so that users will now that there is error