We have created a request offering with an "Approver" field. This field uses a picklist for selecting the "Approver". The picklist is designed as:
Get list data from - Business Object - Profile.Employee
Display field: Full Name
Value field: Full Name
Sort by field: Full Name
We have configured the request offering to use a workflow with a "Get Approval Block". In the "User from Context BO field/ Service Request Parameter" block property, we can select our request offering "Approver" field. Everything appears to work but when the workflow runs, no Approval is created and no Approval notification is being sent to the "Approver".
The option "User from Context BO field/ Service Request Parameter" in the Workflow Approval block only works with the LoginId and not with the Employee Name.
If you change your picklist's "Value field:" to be Login ID this should resolve the issue.