Not able to enable Data encryption

Hello,

We are not able to enable Data Encryption in CRM 2013 Organization. The below generic error message is displayed when I click on 'Data Encryption'.

No errors/warnings logged in Event log. Enabled Trace and noticed the below error.

>Crm Exception: Message: SYSTEM user account not found., ErrorCode: -2147220933, InnerException: Microsoft.Crm.CrmException: SYSTEM user account not found.
at Microsoft.Crm.ObjectModel.ExtraSecurityValidationForOperationsThatWorkWithSensitiveData.GetBuiltInSystemUserId(ExecutionContext context)
at Microsoft.Crm.ObjectModel.ExtraSecurityValidationForOperationsThatWorkWithSensitiveData.Validate(ExecutionContext context, IHttpsValidator httpsValidator, IHttpsValidationRequired httpsValidationRequirementChecker)
at Microsoft.Crm.SqlCellLevelEncryption.OrgDBPrimaryEncryption.RetrieveEncryptionKey()
at Microsoft.Crm.SqlCellLevelEncryption.EncryptionExecutor.ExecuteOnSingleReplica[T](Tuple`2 encryptionForDB, ExecuteEncryptionWithGenericReturnType`1 executeEncryption)

Please let me know if you have any pointers.