Below are the points how traceability report works :
- The Traceability report gives the data based on Test Run.
- A Test Run should fall within the selected Time frame (Past month, Past 6 months etc).
- If Test Run doesn't fall in the selected range, the linked Story will not expand further.
Solution : Your Story may not be expanding further because it is not falling in selected range. Especially "Timeframe". Please change the Timeframe to past like "Past 6 Month" and see if the stories are expanding further.