This could be a broken conductor in the wire, it could have become disconnected behind the outlet plate, there may be signal splitters along the path that have become faulty (or been removed), or it’s just not connected to the signal at the source.

Why is my cable outlet not working?

This could be a broken conductor in the wire, it could have become disconnected behind the outlet plate, there may be signal splitters along the path that have become faulty (or been removed), or it’s just not connected to the signal at the source.

Can coaxial cables go bad?

The connector on either end can go bad, whether it is BNC, N, or some other type. Sometimes the damage will be obvious, like a missing center pin. Sometimes it will be hard to see, like if the solder has come loose loose behind the connector, or the termination was improperly performed in the first place.