Polar 76 EM keypad not working

Hi
In our machine polar 76 EM there is a different problem we are facing, first we had some unknown error as 9.31.1 then we rectified by changing the AR and IAR board but now we are facing another problem is that, we can type the numbers from keyboard for the input measurement and after if we press the equal key, the machine is not showing any reaction which the input values are taken to its brain, its just being idle state. But the movement of backgauge positions are measured and its showing exactly. Also i have attached the image for references. If anyone knows this kind of problem to solve please guide me.