Hi @AnupK
maybe the disabled rule has never been pushed to production?
What do you see when you open the rule in Launch and press the three dots at the top right and click "Compare Revisions"?

You should see a "Disabled" and "Live in production", should your disabled rule have ever been deployed.

Only then you can actually also delete the rule which not possible if it has once been live and the deactivation not been propagated to PROD as well.
Cheers from Switzerland!