I replaced my laptop battery and now the computer won't turn on

Hi,

I am having the same problem with Dell Inspiron N5559. I got a new battery as the old one was not giving enough backup. I was able to switch on the laptop using the new battery and it was charging also. Then I disconnected the charger and it also gave backup for a couple of hours. At this point, I switched it off and then when I tried switching it on the next morning there was no response. I tried replacing the battery with old one and connecting the charger but there no response on the laptop. Even the power button which is on when the charger is connected is also not turning on. Can you anyone please help me identify what the problem could be.

Thanks in advance.