There are a couple of reasons the Requisition may not be in the 'Awaiting my Approval' tab. Please check the below suggestions.
1. If the User's account is set up with Approval flows and multiple Users, the Requisition may have already been approved by another Approver.
Please follow the below steps or click here to View the Audit Log.
2. Also check who the next Approver is, follow this handy link to View the Next Requisition Approver.
3. Check if the Requisition has been Cancelled or Declined. Follow the below steps.
From [Dashboard], go to [Documents] [Requisitions] [Cancelled].
Look for the 'Document number' of the Purchase Requisition in question.
Follow the same procedure to check if it has been declined by clicking on [Declined] tab.