Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I am sorry to hear about the problem... it might signify failure of the central control circuitry of the phone system, especially if the system is not responsive and shows no other signs of life aside from the screen and in other ways.
The only thing I can suggest that might help, is to have the phone system box unplugged for a considerable interval, several hours at least and perhaps overnight. That might give it a 'rest reset' and restore some function and/or the screen's function, hopefully.
Let me know how it goes.