Dear All,

I am currently developing an application that integrates with the Strava API, and I am experiencing an issue when attempting to subscribe to the webhook endpoint using a custom domain.

Here are the details of the issue:

- The webhook works when tested through ngrok (e.g., https://xxxx.ngrok.io/webhook).
- However, when I try to register the webhook subscription using my custom domain, I receive a `503 Service Temporarily Unavailable` error from the Strava API when hitting the endpoint `https://www.strava.com/api/v3/push_subscriptions`.

I have verified the following:
- My server is accessible via HTTPS and has a valid SSL certificate (Let's Encrypt).
- The endpoint `https://domain.com/webhook` is reachable and returns `EVENT_RECEIVED` for POST requests.
- The webhook route is publicly accessible and correctly configured in my Laravel application.
- Firewall rules and server logs do not show any issues or blocking behavior.

I suspect the issue may be on Strava’s side or related to a domain restriction or validation issue. Could you please advise if there are any known limitations or issues with using custom domains for webhook subscriptions?

Thank you for your assistance.