Please accept my apologies. It wasn't clear to me that there's an issue left over from your previous question.
The translation for error [-10311] is "Identity is disabled for explicit login". The fact that the dialog identifies it as an "Unknown error" may be because of an outdated PI SDK client.
It may be that the PI User you are trying to connect with is disabled for explicit login or that explicit login's are generally disabled. Please see the following 2 screenshots.
Please note that we discourage from using Explicit User login. Please see Security Alert: PI Authentication Weakness