Billing order for the subscription based on the service plan the 'Attach Usage Statistics' option enabled (e.g. PACI) was generated, but there are no records on the
Service Usage Details tab.
The payment initially attached to this or some other order was deleted, and due to the bug #PBA-52201 ("All the Service Usage details are removed on a document deletion.") a table "UsageDetail" was cleared.
The bug is fixed in PBA 5.4.17 and PBA 5.5.6. Install the necessary update as soon as possible. After update is installed, the deleted records can be manually restored (copied from log and manually inserted to the database), if BM logs with the verbose loglevel exist.