Check permission
Open Settings, then Privacy & Security, then Motion & Fitness. Fitness Tracking must be enabled there, and each app additionally needs its own access to that data.
If access is turned off, iOS can still collect motion data internally, but apps will not receive those values.
Other common causes
If the iPhone is not carried on your body, for example while it sits at home or in a bag next to you, the motion needed for counting is missing. A device that was powered off for a while or recently restarted can also show a short gap.
In rare cases, restarting the iPhone helps if a system service is not responding correctly.
When a gap is expected
Not every missing number is a bug. An incomplete or missing day can simply mean the device was not carried. An app that treats such days honestly as incomplete, rather than as a flat zero, distorts personal trends less.
Tips
- Check Motion & Fitness in Privacy settings first.
- Restart the iPhone if counting still stalls with permission already enabled.
- Carry the device consistently if you want reliable daily numbers.