AWS Missing credentials when I try send something to my S3 Bucket (Node.js)

Try hardcoding your params and see if you get the error again :

AWS.config.update({
    accessKeyId: "YOURKEY",
    secretAccessKey: "YOURSECRET",
    "region": "sa-east-1"   <- If you want send something to your bucket, you need take off this settings, because the S3 are global. 
}); // for simplicity. In prod, use loadConfigFromFile, or env variables

var s3 = new AWS.S3();
var params = {
    Bucket: 'makersquest',
    Key: 'mykey.txt',
    Body: "HelloWorld"
};
s3.putObject(params, function (err, res) {
    if (perr) {
        console.log("Error uploading data: ", err);
    } else {
        console.log("Successfully uploaded data to myBucket/myKey");
    }
});

Good resource here

I had the same problem until I reversed the two lines:

var s3 = new AWS.S3();
AWS.config.loadFromPath('./AwsConfig.json'); 

to this:

AWS.config.loadFromPath('./AwsConfig.json'); 
var s3 = new AWS.S3();