Thanks for getting in touch! When you create a release, it takes a snapshot of the project's variables and deployment process at that point in time, and uses that snapshot when you deploy the release through each environment in your lifecycle. This ensures that you know what was deployed to Dev is what gets deployed to Prod, but it usually requires a new release to be created depending on what you need to change.
If the change you made was on the variables in Octopus, there's a way to update the variable snapshot of the release to current. In the web portal, this option is under the specific release page. I've attached a screenshot showing this option. However, unfortunately there's no way to update changes to the deployment process in an existing release.
I hope this helps! Don't hesitate to reach out if you have any further questions or concerns going forward. :)