Manage Workflow for service entry sheet Person Responsible

Hello,

I have activated Flexible Workflow for Service entry sheet - lean. Also I configured one step within a workflow assigning role Person Responsible for Service Entry Sheet Release, when creating a SES the workflow generates an error indicating "No agent determined (rule id 'PersonResponsible')". What we want to know is where the system is looking for the "Person Responsible for Service Entry Sheet Release".

Many thanks,