Try hooking the coax directly to your TV and do a scan. Do you get channels? If you do, the issue is with your OTA dongle or the Hopper. If you don't the issue is with your Winegard pre-amp or the antenna, or how you have it wired. Just to be certain, your power supply , that you replaced, has an in and an out coaxial connection.
I can't see the markings on it but it should say something like "to antenna" on one and "to TV" on the other. Perhaps, and this is a guess, you have them backwards. If that part is straight, remember that you have a pre-amp at the antenna location. There is a chance that it has gone south. I know it's all coincidental but it is a possibility.
First, make sure that the power supply is set up correctly, then attach it directly to the TV. If you get channels on the TV you have proven that the antenna, pre-amp, and power supply are all working correctly. Does your power supply have a power on light? If it does, it will tell you if you have power to it. If that light isn't lit, check you power source to it.
Just some things to try.....