ErgoDox not showing up after flashing

[aidalgol]

I just finished assembling my ErgoDox — my first mechanical keyboard, by the way — and flashed the firmware and... nothing shows up on my PC. I can flash the Teensy just fine with the "blink" program, so I don't think the problem is in that stage. I flashed following the instructions on Massdrop https://www.massdrop.com/ext/ergodox/assembly.php and on the github repo for the firmware https://github.com/benblazak/ergodox-firmware (which are the same, only worded differently), using first the precompiled firmware provided, and then again with firmware built from master on my machine. I also tried flashing a .hex file generated by the "configurator" webapp (with the default QWERTY layout) https://www.massdrop.com/ext/ergodox. After each attempt, I unplugged and plugged in the Teensy to my PC, and the device does not show up in the output of lsusb (I am on Debian 7.6), but it does show up when in HalfKay mode as "16c0:0478 VOTI Teensy Halfkay Bootloader".

Any troubleshooting suggestions? I'm at a total loss.

[aidalgol]

OK, I figured it out (a while ago – I didn't only just now figure it out): I had the USB cable plugged directly in to the Teensy to avoid fiddling with stripping the USB cable and soldering it, but it turns out that the holes where the USB cable wires are soldered don't only go to the female USB plug, but also the TWI pins.  The TWI initialisation was never completing when the USB cable was plugged directly into the Teensy, but the keyboard worked as expected once I wired up the USB cable to the PCB.