Error invoking Method 'sendSlack'


I have developed a MeteorJs project which sends some messages on your Slack. (following this tutorial link)

Though it runs smoothly locally and on Heroku, when I uploaded on DigitalOcean I am getting this message:

“[Log] Error invoking Method ‘sendSlack’: Internal server error [500] (f28e39f50692cf61ad0b0a98bfb0e69f709b7d17.js, line 3)”

Any idea why I am getting these?

Is there a way to see the Server log files or the Server console as I assume that I can find some more specific messages.