​@RTHA - Have you tried using the “refresh activity achievements” function?  I know that recalculates segment results, but not sure if it will impact the more global activity achievements like “longest ride” but might be worth a shot.

I recently answered a question like this from another user, and he seemed to indicate my suggestion worked for him:  

Coupla guesses here:
1.) On the activity page (web), click on the three dots, then click "refresh activity achievements".  Give it a few mins to work. 
2.) If that fails, change activity type to something else (anything... hackey sack, foosball, hula hoop, doesn't matter.)  Then change it back to walk.
We have to do things like that in cycling to sometimes straighten out segment rankings.   

This was the topic:  https://communityhub.strava.com/strava-features-chat-5/invalid-longest-walk-ribbon-10023