

In the right pane, find any certificate named Unknown or Communications Server, select it, and then delete it.
In the left pane, select login, and then select Certificates. Navigate to the following directory: C:UsersusernameAppDataLocalMicrosoftOffice16.0Lync
If you’ve forgotten your password or it’s no longer working, use the Microsoft Online Password Reset site to send a new password request to your workplace technical support-typically the person who set up your Microsoft 365 account for you. For more information, see Sign in to Skype for Business. If you’re already using Skype for Business on your desktop, then you can sign in with the credentials from your work or school account. You need a sign-in address and password from an organization that has a Skype for Business or Lync license. How do I sign in to Skype for Business on Mac?
