Passkit-generator library created an invalid .pkpass file despite inputs being (seemingly correct)

Question

I have just started using the (https://www.npmjs.com/package/passkit-generator) NPM library, and I would really appreciate help with this. It is the first (and hopefully the last) time I am working with apple wallet, and it is just so confusing.

After copying one project, I have tried to run the code, and while it generated a .pkpass file, the file wasn't valid, at least according to the https://pkpassvalidator.azurewebsites.net/ checker.

The code of the app is pretty short:

const fs = require("fs");
const { PKPass } = require("passkit-generator");
try {
  (async () => {
    const pass = await PKPass.from(
      {
        model: "./passes/sample",
        certificates: {
          wwdr: fs.readFileSync("./certificates/awdrca.pem"),
          signerCert: fs.readFileSync("./certificates/signerCert.pem"),
          signerKey: fs.readFileSync("./certificates/signerKey.pem"),
          signerKeyPassphrase: "[private passphrase]",
        },
      },
      {
        serialNumber: "[generated at random]",
      }
    );
    pass.setBarcodes("36478105430"); // Random value
    const buffer = pass.getAsBuffer();
    fs.writeFileSync("output/pass.pkpass", buffer);
  })();
} catch (err) {
  console.log(err);
}

The pass.json I am using for this is one of the example ones provided by the apple documentation:

{
  "formatVersion": 1,
  "passTypeIdentifier": "[the pass type identifier]",
  "serialNumber": "8j23fm3",
  "webServiceURL": "https://example.com/passes/", // I don't entirely know what this is good for
  "authenticationToken": "[generated randomly]",
  "teamIdentifier": "[Apple dev team id]",
  "barcode": {
    "message": "123456789",
    "format": "PKBarcodeFormatPDF417",
    "messageEncoding": "iso-8859-1"
  },
  "organizationName": "[Org name of our company]",
  "description": "Toy Town Membership",
  "logoText": "Toy Town",
  "foregroundColor": "rgb(255, 255, 255)",
  "backgroundColor": "rgb(197, 31, 31)",
  "generic": {[contents of the pass]}
}

I was trying to figure this out for the past several hours, but whatever I do, it seems like certificates might be the problem. I tried to test it on my Iphone (sending the generated pass to my email and opening it there) but it did not open. I tested the sample apple documentation pass and it did open perfectly.

I will be super thankful for any help.