By-passing the amp will make the antenna nearly useless unless you are very close to the TV tower(s). It would be better (if possible) to go on the roof with a voltage meter, disconnect the coax from the head of the antenna and then measure the voltage in the coax itself to verify that you have at least 12VDC available. If you do not the problem is inside and if you do the likely problem is the antenna head.
This, of course, assumes the wiring between the amp and the TV is all good. It assumes the TV was working, no work was done in the area and now it's not working.