Coinbase Connect (OAuth2) "The request is missing a required parameter, includes an unsupported parameter value, or is otherwise malformed." - node.js

Question

Dear stackoverflowser,
I'm stying to build an Electron app with Coinbase intergration.
First I'm going to make the server (NodeJS) work with OAuth2.
Every thing works great, but when I want to change the code into an access token with the instructed post request it gives me the following error:
{
error: "invalid_request",
error_description: "The request is missing a required parameter, includes an unsupported parameter value, or is otherwise malformed."
}
I already added https://localhost:3000/auth/coinbase/callback and https://localhost:3000/profile to the valid API URI's.
I wasn't successful in figuring it out after several hours.
My server is this:
var express = require('express');
var app = express();
var fs = require('fs')
var https = require('https');
var coinbase = require('coinbase')
var request = require('request');
var options = {
key: fs.readFileSync('./ssl/coinbase.dev.key'),
cert: fs.readFileSync('./ssl/coinbase.dev.crt'),
};
var client_id = 'gues it'
var client_secret = 'gues it'
app.use(express.static('static'));
app.get('/login/coinbase', function(req, res) {
res.redirect('https://www.coinbase.com/oauth/authorize?response_type=code&redirect_uri=https://localhost:3000/auth/coinbase/callback&client_id=' + client_id + '&scope=wallet:user:read,wallet:accounts:read')
})
app.get('/auth/coinbase/callback', function(req, res) {
var data = {
client_id: client_id,
client_secret: client_secret,
grant_type: 'authorization_code',
code: req.query.code,
redirect_uri: 'https://localhost:3000/profile'
}
request.post(
'https://api.coinbase.com/oauth/token', data, function (error, response, body) {
console.log(body)
res.send(body)
}
);
})
app.get('/', function(req, res) {
res.send('home')
})
app.get('/profile', function(req, res) {
res.send('profile')
})
var server = https.createServer(options, app);
server.listen(3000)
Thanks in advance,
Theo
[EDIT]
I contacted the Coinbase developers and they were surprised that there was no NodeJS example on OAuth with Coinbase, so they added it to their roadmap.

Answer 1

This is most likely caused by one of the following:
You do not have 'http://127.0.0.1:3000/profile' listed as a valid redirect API in your application settings.
You are reusing an authorization code that has already been exchanged for a token.
This section of this page:
OAuth2 Redirect URI
For added security, all redirect_uris must use SSL (i.e. begin with
https://). URIs without SSL can only be used for development and
testing and will not be supported in production.
Contact api#coinbase.com to get that sorted out.