Approval for Interaction Ticket in Service Desk not Working

Approval for interaction ticket in service desk is not working, their is no data showing for approval logs and waiting Approvals in Approval Tab , Approval Definations are set but no data is showing and no approval request is generated how to solve this issue? and how to set approvals for service desk interaction ? Needed help in solving this issue, This is a client requirement to approve interaction before working on it, approvals definiations are set before moving to another phase but it is not working, no data is shown in approval logs and waiting approval /current approvals so how to solve this issue