In order for a user to see the Approvals option for requisitions (or see the Approvals tab within the Requisitions option) in Web Link, the user must:
Have Full Access to the Approve Requisitions option for Web Link listed under the User Permissions List in the User Security option.
Be assigned to an approval sequence (User ID field or Alternate User ID field completed) for an approval tree within the Requisition Options in Accounts Payable, or assigned as the approval tree owner for an approval tree.