No data return when open a new window by click on a button

Not sure what did I miss... In EBS 11.5.10.2.  Create a custom form.

In the master form ( first window, called headers ), It has a button.  if you click on it, it open up another window called class to show the detail.   But not sure what did I miss.  but when I click on the button, it did not query and return all the data from the detail class table with the give headers.header_id.  Can you tell me what did I miss?

a relations called VENDOR_NOT_SONO_VENDOR_NF defined with headers.header_id = class.header_id.  

In Header  on-populate-detail trigger, I have this