Here you can see two headings under Accounting Manager Main Page:
If you want to search invoices with approved status, you will click on Show Invoice Approved
and it will redirect you to https://demo-trunk.ofbiz.apache.org/accounting/control/findInvoices?lookupFlag=Y&statusId=INVOICE_APPROVED
Here you can see all approved invoices, but the status check box is not selected. Check box should be selected for chosen search criteria.