Hey @talha Racheal from the Support Engineer team here 👋
Do you know if you have your own CAA (Certification Authority Authorization) record of domain "productengine.app" on DNS? This will stop us from creating SSL for your subdomain if so.
In order to resolve this you will need to follow this this guide to update your record (specifically adding both "digicert.com" and "letsencrypt.org" to the CAA record) or remove the CAA record from your side. After that you will need to wait until this DNS update is propagated to the world.
If you run into any trouble or have any questions please write into the team so we can take a better look!