VCore 3 End Stops Not Electrically Closing?

Hey all, I'm wondering if someone could help me understand the limit switches (end stops) that came with my rather old VCore 3.0 kit. Specifically, it doesn't seem like my switches actually close the ground and signal pins when physically triggered and probed with a multimeter. Maybe I'm not understanding things with the LED function though... Background: I'm wiring up a Manta M8P (1.0) so am following https://os.ratrig.com/docs/boards/btt/manta-m8p. Checking my limit switches in klipper they never change state when physically triggering the switch (the LED does shine when triggered though). I then noticed the warning on that page that the switches "probably" need to have their white (notionally signal) and red (notionally 5V) lines reversed on one side of the cable so I did that for one axis to test but still don't see any movement on the switch state. Removing the switch and jumping the white (signal) and black (ground) lines leads to klipper telling me they triggered so I know my pinout / config is OK. I then probed the actual switch(es) with my meter and don't see any contact when the switch is closed between the signal and ground pins.... is that expected? Is it possible to burn out the little switch circuit?