Hi,
I would suggest starting the investigation by using curl to try and fetch the dashboard from inside the VM: curl HTTP://localhost:19999. If it works, then for some reason Netdata can not be accessed by another machine. Then, we could look into whether Netdata itself has this restriction (by looking at the configuration) or whether AWS EC2 needs some configuration to allow inbound access. Chances are that if you are using netdata default configuration, then netdata is accessible by any machine, so it must be EC2 specific.
BTW, Welcome to our community! Thank you for posting your questions and be sure to stick around and help a user or two if you happen to have any insight on their questions. We would love to see you how you use netdata 
Best,
Odysseas