Cannot get SD card to work

Hi folks,

I had wired up an SD card socket from Sparkfun:

https://www.mouser.com/ProductDetail/SparkFun-Electronics/DEV-13743/?qs=WyAARYrbSna7AKzdOk0X8g%3D%3D&gclid=Cj0KCQiAsqLSBRCmARIsAL4Pa9TQXhYrFu8L0QQcDVMAQE91NwG4RAm4irzcp8LHGGQq_icz7bBiY6saAuxPEALw_wcB

But I keep getting the message, even with multiple different SD cards, all formatted to Fat32.

"Uncaught Error: Unable to mount media : NOT_READY
    at line 6 col 41
     console.log(require("fs").readdirSync());"

I triple-checked all the connections, and then used a meter to check connectivity, power, shorts, etc. They were all correct.

So I figured it must be the socket. I removed it and soldered this one on in it's place, figuring that perhaps the added voltage regulation circuit might help:

https://www.adafruit.com/product/254?gclid=Cj0KCQiAsqLSBRCmARIsAL4Pa9SFqtMV7P6ijT3YC_O2wkmDjScGyUWDSlxgrcYFvsitDs03yyHVn2oaApQ7EALw_wcB

But I still get the exact same error message. Am I missing something obvious here? Again, I checked all the connections and they're fine. I have a DS18B20 connected to different pins and it works great, so the Espruino appears to be fine. Test program for SD card looks like this:

function onInit() {
  console.log("Connected!");
  // Wire up up MOSI, MISO, SCK and CS pins (along with 3.3v and GND)
  SPI1.setup({mosi:B5, miso:B4, sck:B3});
  E.connectSDCard(SPI1, B6 /*CS*/);
  // see what's on the device
  console.log(require("fs").readdirSync());  
  for (var i in files)
    console.log("Found file "+files[i]);

  var f = E.openFile("log.txt", "w");
  f.write("Testing 123");
  f.close();
  
  f = E.openFile("log.txt", "r");
  f.pipe(console.log);
  f.close();
}