works for me :)

10189.js

var Client = require('./coinbase-node').Client;


var client = new Client({
      'apiKey': 'bTSRsOipbMgBfYb6',
      'apiSecret': 'lzAsP0prLfpGruFBbJPZM1XtBZiD9R5D',
      'baseApiUri': 'https://api.sandbox.coinbase.com/v2/',
});

client.getAccounts({}, function(err, accounts) {
  accounts.forEach(function(acct) {  
      console.log('balancen: ' + acct.balance.amount + ' for ' + acct.name);
  });
});