poweredge firmware upgrade using powershell redfish for IDRAC

Hi ,

I am trying to intiate firmware upgrade from powershell using the dell provided repo that uses redfish.

whenever I invoke the following method  : Set-DeviceFirmwareSimpleUpdateREDFISH 

I get the following : 

{"error":{"@Message.ExtendedInfo":[{"Message":"Unable to verify Update Package signature.","MessageArgs":[],"MessageArgs@odata.count":0,"MessageId":"IDRAC.2.5.RED007","RelatedProperties":[],"RelatedProperties@odata.count":0,"Resolution":"Re-acquire the Update Package
from the service provider.","Severity":"Warning"}],"code":"Base.1.8.GeneralError","message":"A general error has occurred. See ExtendedInfo for more information"}}

although if I upload the firmware package through Idrac web console (IDRAC9) it get through and updates succesfully. 

what I am missing ?