When trying to cluster.openBucket("bucket") getting error CouchbaseError: Invalid input/arguments

connections
#1

####My code:

var config = require("./config");

var cluster = new couchbase.Cluster(config.couchbase.server);

cluster.authenticate(config.couchbase.username, config.couchbase.password);

var bucket = cluster.openBucket(config.couchbase.bucket);

####The error:

/node_modules/couchbase/lib/bucket.js:206
this._cb = new CBpp(bucketDsn, bucketUser, bucketPass);
^
CouchbaseError: Invalid input/arguments

I am able to connect to my local couchbase server with the code.
I cannot connect to an external couchbase server.
Any ideas why?