Can't connect to internet, thot router spoilt, changed out 1 but stil can't connect

[clhh12]

Hi cybertech gurus,

My network connection is as such:
From my ISP modem to a router and 2 lan cables out to 2 pc/laptop (laptop A & pc B).

Today i came back from work, i switch on my laptop, there wasn't any internet. My dad had just switched off pc B after gg online.

Initially i reset the router but i still can't connect to the internet.

I connected the cable straight from the ISP modem to my laptop and i can get a connection. (That's how i can type it here now.)
I figured well, the ISP modem and the RJ45 cable is ok. So it must be the router.
So i went out and bought a router back and i changed it out. However it still can't connect to the internet. The old router is TP-link brand TL-WR740N and the new one is Aztech WL852RT-4.

So if the line from the ISP modem is working but a changed out of the router is did not solved the problem, what could be wrong?

i'm puzzled.

Thanks everyone!