No electrical power

1999 Chrysler LHS, 104,000 miles, V-6, 3.6
Had the starter replaced one year ago.

At first it turned over once and then made loud clicking noises. I removed and cleaned the positive battery cable connection, tried to reach the negative terminal with wire brush but it's hard to get to. Now the car has absolutely no power at all even when I try to jumpstart it. Any ideas on why all power is now gone? Thanks so much for any advice, I'm having a hard time getting information online.