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The workflow might change to another state, or someone gets an email notification, or simply nothing. States can be left in an expired state if that's how the workflow is implemented, and this may often be the case if reporting is used to handle expired states.
A workflow JSON trigger can be added to a custom workflow to listen for the expiry and generate an on-screen notification or a custom email notification.
When a state expires, it may take up to a minute before any changes will be seen, and a page refresh will be required.
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