I have the same problem: Unable to save app.
I mailed nobody so far. I guess after all the reports someone will (hopefully) already know.
I still got no answer and mailed them 7 days ago.
This issue has been escalated to the Ad Services portal team to investigate. I will post an update here when I hear back.
Was able to successfully create a new App in Ad Setup. Working for anyone else now?
Working for me too.