Old battery died, replaced with new AA battery and its stopped workin

my calculator old battery died, so i bought new AA battery and replaced the old one. when you place the battery, it will get on, it will work fine, but once you switch off, it is not getting on.

some times taking out battery and placing it again wont switch on the calculator, if you reverse and place the battery and then you place it correctly , it will work.

also in back of board there is + and - sign on board, with the metal if you connect both, it will get on.

please tell me how to fix the problem.