If you receive this error when you try to remove your existing resources from your Tenent, Then you have to check the Azure subscription status.
Error will say something like,
Remove-AzureRmResourceGroup : 'this.Client.SubscriptionId' cannot be null.
At line:1 char:1
+ Remove-AzureRmResourceGroup -name QlikSense
+ CategoryInfo : CloseError: (:) [Remove-AzureRmResourceGroup], ValidationException
+ FullyQualifiedErrorId : Microsoft.Azure.Commands.Resources.RemoveAzureResourceGroupCmdlet
As I mentioned in the above this error will trigger when you try to remove the resources by using the PowerShell commands.
To verify you can run below mentioned command,
If you check this in the Azure portal, you will see,
To resolve this issue you can set the Azure subscription manually by running Select-AzureRmSubscription command or remove the Resource groups by login into the Azure portal.
I preferred the second option as it worked for me few times.