Does your coaxial off the antenna amplifier plate go to a switch-box and then the TV?
If so, disconnect the coaxial cable going to the switch-box and connect it directly to the television coaxial input. Make sure the amplifier is turned on (LED is lit). Now set up television to "antenna" and do the auto-search.
If the stations are found the problem is the switch-box (wrong buttons pushed/bad cable connections/or otherwise).
Did you remove the amplifier-plate screws, and pull the plate slightly away form the wall to make sure the coaxial-cable is tightened correctly to the back of the plate power injector? If not no power to antenna amplifier or good signal connection.