You need to trigger several workflow runs before checking if the cache is effective. {% data variables.product.prodname_actions_runner_controller %} requires an `Available` PV to be reused for the new runner pod, and a PV becomes `Available` only after some time after the previous runner pod that was using the PV terminated. For more information, see [this discussion](https://github.com/actions/actions-runner-controller/discussions/1605).