If it says poor or no signal, it would suggest there is not enough signall.
The various chs are carried on a handful of signals, and some are a bit stronger than others in some areas or effected by landscape etc. So it's very poss to have reception of some chs but not others.
Signal issues can be related to a bad cable, maybe one that connects to the wall socket, or one that connects to another device. Plugs and sockets also come into this. A single bad aerial plug or socket can wipe up many chs even if the signal is strong.
Aside from cables, plugs, sockets, do you know if the signal from the aerial is good? How was the signal on the old TV....i