Hi @mehdi adibi
According to your error message, it seems you are have not only one domain controller in your Skype for Business Server.
In this case, we firstly recommend you check if you have multiple domain controller. You can run the command "Get-CsAdDomain -Domain "DOMAIN.com". If the Skype for Business Server is 'looking' at the wrong domain controller, it recommends you remove the extra domain controller(DC) from your server. For more details about how to remove, you can refer to:
In addition, please make sure your DC OS are met this article's requirements.
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