If you are trying to retrieve your steps data, because you changed your phone or because you installed the app anew, check if those are correctly saved in Apple Health first.

If so, try to go in sync and import the data again in StepsApp.

How to go in sync:

• Open StepsApp
• Go to "Settings"
• Tap on "Apple Health"
• Turn On Apple Health Sync or Re-sync again 

Find here a video about how to recover steps data: https://www.youtube.com/watch?v=CCTHToivXJQ