To view health-related data such as Heart rate on your Strava Dashboard, you have to explicitly give access to Strava to use Health-Related data.
Here are the steps to authorize permission for Health-Related data on Strava:
Login to your Strava Dashboard.
Tap on your Profile image on the top-right and click on "Settings"
Click on "Data Permissions" from the menu on the left.
Click on the "Allow Access" button.
You will see a Pop-up Confirmation Box. Click "OK"
You will now be able to see your Health-Related data on your Strava Activities.