Steps and intensity minutes not tracking

I have had my Vivoactive 3 since Christmas and have never had an issue.  Today it won't record steps or intensity minutes.  I went in to reset the watch and there is no reset option the only option I have is to restore defaults - which I would rather not do if I can  help it.  Activity tracking is turned on.  Any suggestions or anyone else having the same issue?

  • I have the same problem. Suddenly the intensity minutes seems set to zero. I ran for nearly an hour this morning including some proper hills. No intensity minutes. 

    There have been several mentions of this, but no apparent definitive explanation(s) from Garmin.