Claims are directed an approver via the Approval route assigned to a user in their record.
Check the Approval route to see if the approver is included in error.
Check the user, to ensure that they are in the correct Approval route.
It may be possible that the expenses in the system were submitted before the user was added to the approval group.
To test this, send through a new expense and see if it goes to the correct approver.
Once the cause has been established, the incorrect approver can reject the expenses, or an administrator can do this on their behalf, so that when they are resubmitted they will follow the amended routing process.