Not working. No display. Better also changed. what should I do?

same problem occured my casio fx-991es plus. i changed battery same problem occured not turn on my calculator but working while solar. so i opened my calculator i check the wire connection solar wires are connected properly and battery black wire it mean negative line cut down. i fixed that issue now my calculator working finely. thanking you.

On the back there will be a “P“ button in the middle. Press it and see if there is a difference.

I saw that the calculator was solar, so then I took my device and turned up the brightness and faced it to the front of the calculator. It started turning on

As it’s screen is not showing anything; Consult with any technical expert as there may be some internal faults which can’t be solved verbally.

Same thing also happened with my calc. So i was searching for the reset button but couldn’t find any at the back. So what i did was i tapped the calc around the solar plate area with my fingers three four times and then pressed the power button. And it turned on.