subscription_id has disappeared

[astrogation]

I’m facing an issue.
I run a website where users subscribe to a service.

After creating the subscription on PayPal, users are redirected back to my site, but the subscription_id is missing from the redirect URL. In the sandbox environment, the subscription_id is present, but not in the production environment.

How can I make the production environment behave like the sandbox?

Here are the redirect URLs:

Production:
https://my_site.net/completed.html?token=28A81719VJ123456&ba_token=BA-123456&PayerID=123456

Sandbox:
https://my_site.net/completed.html?subscription_id=I-4PAJ3U123456&token=28A81719VJ123456&ba_token=BA...

Here’s how I create the subscription:

1. Send a POST request to v1/billing/subscriptions with the pre-created plan.
2. Log in to PayPal via the response link.
3. Complete the payment on PayPal, then return to my site.
4. Use the subscription_id from the URL and send a POST request to /v1/billing/subscriptions/{id}/activate.