I am currently hosting my website on amazon elasticbeanstalk and I purchased a domain from namecheap.com then I followed the steps here. On AWS route 53 I created a hosted zone and an Alias record then on my namecheap account I selected custom DNS as my DNS servers and inputted the values I got from AWS route 53. Now after 24 hours I can access my website from www.domain.com but not from domain.com. I opened up a terminal and I pinged domain.com it says "unknown host domain.com" but pinging www.domain.com works. I don't know why.
For this you need to create an another Record Set with empty name i.e. leave the name field blank and provide the value same as www.yourdomain.com (your IP address).
Please do note that both the values on WWW and non-www should be the same.
Hope this would solve your problem!