There was an issue during Friday with that challenge. To fix that you had to leave and join the challenge again. That is too late now. If you leave a challenge that has ended you can't join it again.
It might work if you make an edit to the run activity. That has worked for some, but I don't know if it will work now when the challenge has ended.
Tip for the future: Check the challenge status right away. Do not wait this long. For challenge you must do it during the challenge period. Afterward the period you will have to contact Garmin Support to get help. You and we can't do anything now.
