This is most likely due to various perspective and reallocation rules not being configured properly.
When containers are first configured within the platform, the resources and allocation reports should work out of the box based on default configurations. These basic configurations include using namespace and pod name for task family and task in a Kubernetes report.
The Cost History for containers, however, will not work out of the box as it requires additional setup.
Otherwise, the Cost History report will simply show "Assets Not Allocated".
While the Container Cost History report is still supported, we recommend you switch over to the Kubernetes Cost History report as it's built on a newer platform where container cost distribution rules and perspectives are not necessary.