I'm trying to get app/uninstalled to uninstall the application, but the webhook doesn't send it back to me. I see that the webhook has been registered successfully. SSL has been successfully installed. What could be the reason?
Try updating the webhook address to something like a requestbin.com endpoint to test. If that works, something on your endpoint is probably an issue.
Also noticed that you are trying an unreleased version 2021-10, try going lower to make sure that's not an issue