Error in generating approval list in iProcurement Requisition

We are using AME  for Purchase Requisition approval. Requisition created from Purchase Requisitions form are being redirected to approvers correctly but when we create requisition from iProcurement page and Submit it then we get below error message.

"You do not have the authority to submit this requisition. Click on Manage Approvals button to add an approver."

Approval workflow is not triggered at all, there is no wf_item and key in Purchase requisition table.

We noticed if Job and Position is assigned to Requestors employee record and Requestor has approval limits as per Position and Job then approval List is getting generated from iProcurement page but if Position and Job are not assigned then we get this error.