I had a '96 for about 20 years (it seems anyway).
Seemed every time I didn't have it turned on for awhile, the screen would be blank when I went to use it.
I always had to do deep surgery to get it to work:
1. Take it apart all the way to where I could pull the keypad out.
2. Clean the fingers on the keypad, and where they landed on the circuit board with alcohol and q-tips.
There's going to be a little silver wedge that holds the display at an angle. Make sure you pay attention how that sits in there before you take it out. I actually drew an arrow and the word "out" on it after about the second time.
I would get residue on the q-tips, don't ask me how. Smoke free house here and it never went outside.