I've just finished soldering the provided ethernet kit for the Teensy 4.1, and began trying to test it. I connected the breakout ethernet board to the teensy via the ribbon cable, and began some basic tests (source code down below). However, the program fails at the linkStatus check, and additionally I notice the light on the ethernet is port is not lighting up - the ethernet cable itself is fine, and works for a similar Arduino Uno program.

I'm wondering what the best way to troubleshoot this is. I'm not very experienced with such fine soldering, so maybe my soldering job (pictures attached) damaged something? I have a spare ethernet kit, but would rather try and diagnose what I did wrong before possibly repeating that mistake on my remaining spare. I should note that the ribbon cable connection seems pretty loose to me, if that matters.

#include <SPI.h>
#include <NativeEthernet.h>

const int led = LED_BUILTIN;
byte mac[] = {
  0xA4, 0xE9, 0xE5, 0x0F, 0xC3, 0x3D };

EthernetClient client;

void setup() {
  pinMode(led, OUTPUT);
  // Check for Ethernet hardware present
  if (Ethernet.hardwareStatus() == EthernetNoHardware) {
    Serial.println("Ethernet shield was not found.  Sorry, can't run without hardware. :(");
    while (true) {
      delay(1); // do nothing, no point running without Ethernet hardware
  if (Ethernet.linkStatus() == LinkOFF) {
    // Code fails here!
    Serial.println("Ethernet cable is not connected.");
Solder job:
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