I followed through.
Set-AzureADUserManager -ObjectId "df19e8e6-2ad7-453e-87f5-037f6529ae16" -RefObjectId "df19e8e6-2ad7-453e-87f5-037f6529ae16".
No Luck. Through script also unable to do.
Get-AzureADUser : Cannot bind argument to parameter 'ObjectId' because it is null.
At line:7 char:61
+ ... ger -ObjectId (Get-AzureADUser -ObjectId $row.'User Username').Object ...
+ ~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidData: (:) [Get-AzureADUser], ParameterBindingValidationExcep
tion
+ FullyQualifiedErrorId : ParameterArgumentValidationErrorNullNotAllowed,Microsoft.Open.Azure
AD16.PowerShell.GetUser.