This occurs because a few of our install and update packages are signed with an older certificate. You might see an 'invalid certificate' error when installing Office for Mac 2011 or Lync for Mac 2011. Under App passwords, click Create a new app password. To fix this, get and enter a unique app password to sign in. If you have two-step verification turned on, you might get an invalid product key error because Office doesn’t prompt you for the extra security code during activation. Get an app password for two-step verification If you can, open an application like Word and click Help > Check for Product updates. In many cases, updating Office will fix the problem. In the Get Started wizard, click Sign in to an existing Microsoft 365 subscription, and sign in with the email address that’s associated with Office. Open an Office application and click Activate Now. Instead, sign in with the email address that’s associated with Office. If you have a Microsoft 365 subscription, you can’t use your product key to activate Mac 2011. Sign in with a Microsoft 365 subscription If you’re getting an invalid product key error, try these solutions.
