404 Not Found when creating new notebook

[emptycrown]

On my EC2 instance, I ran the quickstart instructions, and all the Docker containers went up fine. When I access my server through the browser, the notebook comes up fine. However, when I go to create an new notebook, I get the following:

Checking docker logs for that container yields the following:

[W 07:38:29.395 NotebookApp] Blocking Cross Origin API request for /user/KUH9vx1MsASw/api/contents.  Origin: http://ec2-xx-xx-xx-xx.compute-1.amazonaws.com, Host: localhost:8000
[W 07:38:29.396 NotebookApp] Not Found
[W 07:38:29.396 NotebookApp] 404 POST /user/KUH9vx1MsASw/api/contents (xxxxx) 1.37ms referer=http://ec2-xx-xx-xx-xx.compute-1.amazonaws.com/user/KUH9vx1MsASw/tree