HP34C display issue

[dmh]

Is it a solderless model?

If so, I've had luck pushing the display down (ie into the board wedge if the calculator is standing upright) to ensure it connects properly. Even a tiny amount can make a difference (1mm or less).

You don't need to take the halves apart either as there is room when you remove the screws and split the top to reach in with something and apply some pressure.