Heroku deployment with mongodb atlas failed

[Forest]

Thanks! @sampreeth. Your explanation is awesome and helped me fix the problem!

There are few tips for someone’s need.

For Step Three, if you do not really understand. Please check the below link. And Watch 12:00-20:43. About how to set up and check MongoDB atlas link.

Deploying an Application on Heroku with MongoDB Atlas: Example NodeJS application

For Step Four,
I entered the Key as MONGODB_URL