If you see an error message that says, "An unexpected error has occurred while connecting to Grammarly" or "Unexpected server error" when logging in to Grammarly in Word or Outlook, and at the same time the Grammarly Editor at app.grammarly.com works fine for you, simply click Cancel instead of Log In.
If the issue persists, please read this article.
If you use a proxy, check whether it requires authentication. Your system administrator or IT department may help with your proxy configuration. If authentication is required and you haven't logged in yet, specify your login details by clicking Grammarly on your Word toolbar > About > Proxy settings.
If after submitting your Grammarly login and password you see an error message that says, Proxy authentication required, click Proxy settings to specify your login details.
If you are logged in and need to change your proxy settings, navigate to Grammarly on your Word toolbar > Settings > Proxy settings as shown below.