You are limited to a single callback domain per app. When this has been asked in the past, the recommendation was to create a second Strava account and get a new API key on that one. With the new API/User limits that makes things a lot more difficult and annoying unless you’re the only user. Otherwise you would need to go through the app approval process which seems to take a very long time. Unfortunately since you are trying to retrieve your own activities, I’m guessing a new Strava account/API key in single player mode won’t solve the problem for you since you are probably trying to retrieve your own activities…

The only other idea I can think of is to set up some kind of forwarding service on your earlier site. On your run blog server, set up something to accept API requests from the ride blog server. Then instead of directly querying the Strava API from the ride blog, send the request to the run blog, which submits the request to the Strava API and returns the result back to the ride blog. Admittedly that is a big pain, and opens up some security issues. I’d be interested to hear if anyone else has another option.

Yes, as you say it’s just my own activities I’m trying to retrieve.