After replacing the controller module or NVRAM module for a storage system that you previously configured to use Storage or Volume Encryption, you must perform additional steps to provide uninterrupted Encryption functionality. You can skip this task on storage systems that do not have Storage or Volume Encryption enabled.
ONTAP 9 NetApp Encryption Power Guide
Use one of the following procedures, depending on whether you are using onboard or external key management:
Restoring onboard key management encryption keys
Restoring external key management encryption keys