Workflow & no. & activity & role '&': No agent found

What causes this issue?

If the definition of rule &V4& requires that the rule resolution must
provide agents (indicator <LS>Terminate if rule resolution has no
result</> set in the definition), the workflow was stopped and set to
status <ZH>error</>. If the definition does not consider it an error
that the rule sometimes does not provide agents, a warning is logged
and the workflow continued.

How to fix this error?

Check the information logged by the rule and change the rule definition
as necessary.

Error message extract from SAP system. Copyright SAP SE.