Run '&1' has the status '&2' and so cannot be restarted

What causes this issue?

If you cannot restart an ECS run, there are two possible causes:
ECS run &V1& is part of a mass run that was processed successfully.
ECS run &V1& has the <DS:DE.GLE_DTE_ECS_PP_RUNSTATUS>status</> <ZK><LS>
Undefined</></>.

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.