Have you checked all connections of the coaxial cables?
Starting with connection of coaxial to antenna-head. Remove, clean, and reattach. Is cable secure to connector on that end?
Remove screws and pull plate inside slightly from wall. Are cables there tightened to back of plate and cable tight to cable connectors? Wires to power injector plate connected correctly (same for cables)?
If you have a switch-box disconnect coaxial (input to box from antenna plate) connect it directly to Television cable input. This will by-pass switch-box if problem there.
Make sure that cable end connection is tight and connected to TV input tight.
Indicator on amplifier power does not always mean amplifier is working when LED is lit. Check for 12+ volts on coaxial connected to antenna-head.
Since it worked before a failed amplifier, or a loose connection or cable end have to be the culprit. I never use cheap cables since the end connections can easily pull loose and loose connection. Normally wiggling the suspect connection will change signal to TV.