Agent determination for step '&1' failed

What causes this issue?

An error occurred when determining users for step &V1&. This error can
be caused by a problem in the resolution of a rule for agent
determination. See the additional messages within the workflow log.

System Response

If no recipients could be determined because the responsible agents
determined do not belong to the possible agents of the task, the work
item without recipients is set to the status <ZK>ready</>.
If an error occurs in the execution of the rule for agent determination
and if the corresponding indicator is set, the work item is set to the
status <ZK>error</>.

How to fix this error?

Remove the cause of the error and start the workflow again using the
administration environment.

Procedure for System Administrators

The following agent determination failed: &V2&
EXE,,Recipient
NOT,,Notification when editing is complete
LED,,Notification of missed latest end
LST,,Notification of missed latest start
DED,,Notification of missed requested end

Error message extract from SAP system. Copyright SAP SE.