Do wires go bad?

Wires can break if they are moved regularly. Any metal item can suffer from metal fatigue if it is bent repeatedly, and copper wire is no different.

In places where vibration or repeated bending is an issue, stranded wires are used in place of solid ones, with finer strands used for more strenuous applications. Even a stranded wire can fatigue and break.

You may have developed an oxide layer or have an insulating contaminant over the exposed parts of the wire that you were using. Try cutting and stripping both ends and test again.