Maybe it would work if there was a broadcast that was getting through jamming into the First Order systems.

“The Voice of the Resistance” like this : https://www.youtube.com/watch?v=HkGvYcb36hg which was being sent from the Republic capital (like the BBC Empire Service/World Service).

It could be heard in the camps Jakku and maybe by some fluke get picked up by Finn’s helmet speaker.

It could also be broadcasting in the castle when the weapon is fired and then suddenly be cut short.