No, the viewfinder is not dark... I can see through the mirrors and the lens.
The shutter is opening...and closing perfect. I tried with different speeds and I tried it also taking the lens off,and I can see that the mechanism is working fine. That is why I think that maybe the sensor is the problem... Is this common after 3 years of use? The problem appeared suddenly after taking a picture. Maybe it is something electric given that at that moment the display on the change to classic automatically...
If the sensor is the problem, is it better to buy new one or to change camera?
Marty thanks for the help, any suggestion will be welcome.