If you are using Workflow Manager 1.0 on SharePoint, you may face problems of workflows failing to run due to unexpected expiration of Workflow Manager and Service Bus certificates 5 years after the initial setup. This happens because the certificates that are generated during the setup do not get updated automatically after they expire. It may appear to be a minor issue which could be resolved by renewing the certificate, however you will get stuck once Workflow Manager expires and stops you from renewing.
Even though renewing certificates is not a difficult task, it may get complicated once you are prohibited to renew them after they expire. The reason is while active, Workflow Manager PowerShell checks certificates and it is not possible to establish connection between farms and Workflow Manager with an expired certificate. The error message you will receive while working with PowerShell and in the SharePoint logs will be as follows:
“Certificate requested with thumbprint … not found in the certificate store”