Couple questions:
When you say swapped the headshell with another cartridge, do you mean a different headshell or are you swapping a different cartridge onto the headshell you rewired?
Do you have an ohm meter with which you can check continuity from headshell to RCA outputs?
If you have an ohm meter, this should be simple. It sounds like you have a faulty connection at the headshell to me.
The Concorde Pro S has a built in headshell, I am not sure what to call it but its an 'all in one'.
I do have an ohm meter but assuming I am a 10 yr old... I see on the arm 2 pins on top, 2 pins on the bottom. What should I set the ohm meter to? And if I touch the top left pin, where does the other lead go on the interconnects, inside or outside? Sorry for the really simple questions, I have just never checked it.
The Amazon cart came on a headshell with the 4 wire attached.