Is your activity set to "only you" or "followers only"?  If so, it won't show up in the leaderboards.  Only activities that are set to "everyone" will show in the leaderboards.  Another thing is if part of the segment (usually the start or end) falls within your privacy zone (if you are using one), it won't show up either.  The last thing I can think of is to give it a little time.  Sometimes Strava has a bit of a delay before efforts get updated in the leaderboards.  

Not sure why the solution was accepted?  My settings are open to everyone. I have waited 48 hours, the segment is not close to my privacy zone either but has still not updated?

@Sigmund - Can you post a link to the activity?  There may be some other reason it isn't showing in the leaderboards that might be apparent if we can see the specific activity.

here you go https://www.strava.com/activities/10922049242 PR on New A14 cycleway from Girton (5:15) thank you

@Sigmund - Two ideas.  First, trying refreshing the activity achievements.  Do this from the web by clicking on the three dots on the left of the activity and selecting "Refresh Activity Achievements".  This should force the system to re-analyze your activity.  Give it a little time to see if the times show up in the leaderboard after doing that.  If that doesn't work, my 2nd idea is to submit a support request (https://strava.zendesk.com/home) and see if the Strava techs can figure it out.  

Success! I changed the activity from ride to canoe, waited a few minutes changed it back and it updated! It was a recommendation from the support page you referenced above. Thank you.