Your device stopped counting steps? 

In this case, we advise to run a general check up to ensure accuracy:

Check Motion Sensor setup:

• Open Settings App
• Tap on "Privacy"
• Tap on "Motion sensor" and enable it for Health and StepsApp

Check Apple Health setup:

• Open Settings App
• Tap on "Privacy"
• Tap on "Health"
• Tap on StepsApp
• Turn on all

Re-synch in StepsApp, if you have e.g. : an Apple Watch or other third party device:

• Open StepsApp
• Open Settings
• Tap on "Health" and re-sync again