You know that you’re supposed to hold down home WHILE you are plugging it in right? You mentioned holding it down before plugging it in, dunno if that was just a different choice of words.
Do you have a multimeter to test the wire connections? First thing I thought of was perhaps the Home buttons of the PCBs aren’t connected properly to the imp or to the button or the microswitch of the home button is going out so it’s not working. That doesn’t explain why it would show up as an “Unrecognized USB device” though.
Both of those PCBs should work fine with a PC. You’ll usually get an “Unrecognized USB device” if the D+ Green and D- White wires of the connection are mixed up. Considering you’re using an RJ45 to USB connection, it could mean that one or both of the signal (D+ and D-) wires on the network jack side weren’t crimped properly and isn’t transmitting when plugged into the jack
When you plug it in to any USB source does the LEDs for the 360 board light up?
Have you verified that the wires going into the screw terminals on the Cthulhu are all solid and aren’t coming out or loose?
Having a multimeter means you can check the ground is flowing thru both boards, that the voltage is powering both boards, that there is no signal loss from any of the 4 wires from USB (Ground Voltage D+ D-) from one point to another, you can check the RJ45 to USB cable is correctly crimped. etc etc etc. If you have a multimeter, you can literally continuity test every point from one step to another to narrow down the potential issues.
Also, whomever padhacked that fightpad/brawlpad shouldn’t be putting glue on top of his solder points, but glue on the wire next to the solder points, this allows someone not only to make corrections on the solder point if necessary without tearing the glue off and risking lifting a trace, but also prevents the wire from being lifted up.
I’m all for you potentially fixing your own issue here, but if you don’t have the tools to do anything about it, I’d just suggest taking it to another modder.