Error disabling welcome messages

I have a Team with 10 channels and I need to disable sending emails in all case: when a new user is added...

I'm following this steps to disable the initial emails and when I finish the step 6 I'm obtaining a message with somethig like this: "WARNING: The command completed successfully, but no configuration value has been changed from
"mygroup_objectid"" . 

1. $groupName = "<Replace Group Name>"
2. Set-ExecutionPolicy RemoteSigned
3. $UserCredential = Get-Credential
4. $Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection
5. Import-PSSession $Session -DisableNameChecking
6. Set-UnifiedGroup $groupName -UnifiedGroupWelcomeMessageEnabled:$false

How can I solve this?

Regards