Strava only allows one webhook subscription at a time and the issue might be that the trigger node is not deleting existing subscription. So if you test the Strava trigger node before activating the workflow, it might not work.
While we work on fixing this, could you try turning on the ‘Delete If Exist’ option? If that doesn’t work, can you try manually deleting any existing subscription and then trying to activate the workflow?
You can find information about deleting a subscription iby following Strava Developers or you can also do that with the workflow below: