The CloudHealth platform makes use of AWS API's, and cannot collect files which are not in the Standard storage class.
Please review the storage class of historic CUR files and restore the most recent version for each month if you wish to have historic costs visible in the platform.
For further information regarding storage classes and API access, please see the following AWS documentation: https://docs.aws.amazon.com/cli/latest/reference/s3api/get-object.html