Hi, I'm Nathan.Sorry to hear that you're having trouble, but I'll do my best to help you. Please give me a few moments to review your details here.
What amps are you using?Could you try disconnecting the speakers (don't let the wires touch), but leave the wires connected to the amp on the other end and see what happens? This would tell us if there is a short in the wiring that is tripping a protection circuit on the amp.
Different speakers on the same cords?Can you test the logan speakers independently, one of them may have an internal fault.
That depends on the amp really, but most are not built to drive a single speaker, especially a 4ohm load. You could try a bridged connection IF your amp supports that.
+ on one channel to - on the other.