If your LDS (Local Discovery Service) certificate has expired, you can renew it as follows:
Delete the certificates in C:\ProgramData\OPC
Foundation\UA\Discovery\pki\own. But do not delete the
own folder.
Stop your DataHub instance.
Restart the UALDS service.
Start your DataHub instance.
You may have to also stop and restart any other OPC-UA servers that register with the LDS.