Thanks for asking this question. Any changes you make to your default settings won't be applied retroactively to previous activities. However you can edit those activities individually and change the privacy settings.
Check out the information and instructions here
Let us know if you have further questions.
Thanks for posting about this. I would recommend double checking your map visibility settings.
We have recently made a change to our map visibility settings for all athletes where the first and last 200 meters of your activity maps will be hidden by default. If a segment attempt ends or begins in an area hidden by your map visibility settings, the effort will not be placed on overall/public leaderboards. You will not receive a CR, XOM, or Local Legend for these efforts. However, you will still be eligible to receive personal records on these segment matches.
If you wish to change your default preference, learn more here.
If you wish to update an individual activity, learn more here.
To read about Map Visibility, please refer to this article. And for more information on all of our privacy controls, please visit our privacy center and take the time to ensure your selections in Strava represent your intended experience.
Please let us know if that's helpful.