If the corrrect expenses are not appearing for an Approver, please check the following:
Both the claimant and approver are in the same dataset. You can do this by hovering the mouse over the Expense tab in Workspace, and ensure that both have access to the correct one.
Where the approver has permission to approve On Behalf of another user, it may be that they have a different one selected in the Approve screen than required for this approval.
If the relevant Expense Type might have a specific approver nominated that could affect who approves it (Settings, Expense Types, select the relevant Expense Type and check the Approval field).
If the expense was submitted before a change to the approval route, they these will not be visible to the new approver as only new claims will take the changes. There are two alternative actions in this instance:
Unsubmit the claim and then resubmit it via the History area.
Grant the new approver permission to Approve on Behalf of a user in the Approval route.
If the expense was submitted (or resubmitted) after the change then further investigation will be required. A useful option is to use the Export feature for both Users and Approvals as this allows you to cross-reference more easily.