I can't find the problem when deploying to Heroku. I have already reviewed the code but to no avail.

Apparently, it is something related to some request that is not error handling:

I suspect 2 snippets of the code, because when removing the file they are, the deploy happens normally.

The snippets are:

Reading a .p12 certificate

let cert = fs
    .readFileSync(path
      .resolve(__dirname, `../certs/${ process.env.GN_CERT }`));

Or generating a buffer with the credentials:

 const credentials = Buffer.from(
    `${ clientID }:${ clientSecret }`
  ).toString('base64');

Note: clientID and clientSecret are strings.

ERROR:

2022-04-23T22:13:30.578225+00:00 app[web.1]: (node:22) UnhandledPromiseRejectionWarning: Error: connect ECONNREFUSED 127.0.0.1:80
2022-04-23T22:13:30.578225+00:00 app[web.1]: at TCPConnectWrap.afterConnect [as oncomplete] (net.js:1145:16)
2022-04-23T22:13:30.578225+00:00 app[web.1]: (Use `node --trace-warnings ...` to show where the warning was created)
2022-04-23T22:13:30.578305+00:00 app[web.1]: (node:22) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error either by throwing inside of a sync function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)
2022-04-23T22:13:30.578341+00:00 app[web.1]: (node:22) [DEP0018] DeprecationWarning: Unhandled promises rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

I would appreciate it if you can help.