nokia 7210 supernova phone, screen goes dark

Hello,
After I turn on the phone, the screen goes dark. As soon as I press a key, the screen lights up briefly and then goes dark again until I press a new key. The battery is new, charges well and holds up well.
How could I solve the problem?
The problem appeared suddenly, until then everything had been ok.

Thank you and best regards,
Vasile GRIGORE
Romania