|If you previously had no problems connecting with a different computer you just replaced with the one you mention then that leaves the computer as being your most likely culprit. In which case, I'd contact whomever you bought it from and insist on them figuring out, and fixing the issue.|
If your internet is working fine otherwise, then it's not a network issue guaranteed.
If it's not the computer, and your internet is otherwise working correctly, that leaves only the ISP.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.