I was new to Load Balancer. I managed to make my Elastic Beanstalk work and host my backend by turning Public IP Enabled in the my elastic-beanstalk environment's configuration. Certainly, this QnA & this article were helpful after going through bunch of webpages. So, the Instance has not sent any data since launch. issue was solved via this solution.

However, the Severe status is still there but with different errors (I tried changing Proccess's port to Port 80 and Protocol to HTTP):

• 100.0 % of the requests are erroring with HTTP 4xx. Insufficient request rate (12.0 requests/min) to determine application health.

• Process default has been unhealthy for 12 minutes (Target.ResponseCodeMismatch).

But, these issues are pretty much expected since I am hosting my backend which doesn't have any method or page at it's root endpoint i.e. /. Therefore, when healthchecks is requesting via GET method at my-env.us-east-1.elasticbeanstalk.com/, it returns 400 status. To solve this, you need GET method at your root endpoint which must be free from any authorization wall. Since I don't need it and hosting only backend, I changed my HTTP code in Process to 400-499 from 200 to skip this and resolve Target.ResponseCodeMismatch.