Flow activation after change set deploy
Key Takeaway
By default, a flow in a change set arrives in its destination org inactive, even if it was active in the sandbox. You must activate it manually after deployment.
By default, moving a flow from a sandbox to production with a change set leaves work to do: an app builder must check the flow in production and activate it manually. A production-only setting can deploy processes and autolaunched flows as active instead, but only when flow test coverage requirements are met.
Flow versions in a change set
A change set can include only one version of a flow. If the flow has no active version when you upload the outbound change set, the change set uses the latest inactive version.
Deploying or redeploying a flow with a change set creates a new version of the flow in the destination org, so each new deployment adds a version rather than replacing one. Repeated deployments leave several versions of the same flow in production, so confirm that you are activating the correct version.