Change line 13:
$WAFV_Errors .= WAValidateRQ((isset($_POST["Send_enquiry_group_Enquiry_type__1"])?$_POST["Send_enquiry_group_Enquiry_type__1"]:"") . "",true,3);
to:
$WAFV_Errors .= WAValidateRQ((isset($_POST["Send_enquiry_group_Enquiry_type"])?$_POST["Send_enquiry_group_Enquiry_type"]:"") . "",true,3);