Expense claims are directed to an approver via the approval route assigned to the user. Check the following.
Check the approval route to confirm the correct approver is assigned.
Check the user's record to confirm they are on the correct approval route.
The expenses may have been submitted before the user was added to the approval group.
Submit a new expense to test if it routes correctly.
Once the cause has been identified, the incorrect approver can reject the expenses, or an administrator can do this on their behalf. When the claims are resubmitted, they will follow the updated routing.