Rubicon, thank you for your reply. I finally got it to work...being a newbie to travel trailers and the whole RV thing, I made the newbie mistake.
I never try turning on the faucet before turning the pump. As soon as I turned on the switch and the pump didn't run, I thought it was not working. I tested the voltage on the switch and I got nothing. I then tested the voltage on the drain pump by the shower and I got 12v. So I thought there must be a line power issue somewhere.
I did more googling and one post on another site mentioned that the pump won't turn on where there is enough pressure in the line. So...I turned on the faucet and let some water out and then turn on the switch again and it kicked on...
I guess it was the water pump safety mechanism prevented the water line from over pressurizing. When the pump was running, I measured the voltage again and I still got nothing. I guess the wires on the switch are the negative wire which completes the return, therefore, no voltage reading.
This is a newbie mistake. Sorry for posting. I hope other newbie won't make the same mistake I made.