It's not clear whether you have had reliable reception with the current antenna, amplifier cable and TV. If you haven't had any reception with this combination of equipment, verify that the TV tuner is set to scan for 'air' or 'antenna' signals, not 'cable' which is almost always the default setting from the factory.
If you have had reliable reception and it failed suddenly, then check that the tuner has not been switched back to cable mode... If that checks out and you still have trouble, try this test,
http://forum.tvfool.com/showthread.php?t=13646