Fail to add admin User for AzurePack

When I try to add admin user use powershell command Get-MgmtSvcAdminUser, I got bad result:

Get-MgmtSvcAdminUser : 未能使用提供程序“RsaProtectedConfigurationProvider”进行解密。提供程序返回错误消息为: 未能打开
RSA 密钥容器。 (C:\inetpub\MgmtSvc-AdminAPI\web.config line 67)
所在位置 行:1 字符: 1
+ Get-MgmtSvcAdminUser
+ ~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Get-MgmtSvcAdminUser], ConfigurationErrorsException
    + FullyQualifiedErrorId : System.Configuration.ConfigurationErrorsException,Microsoft.WindowsAzure.Config.PowerShe
   ll.GetAdminUser

translate it to English: Failed to decrypt using provider 'RsaProtectedConfigurationProvider'. Error message from the provider: The RSA key container could not be opened.

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