See what endpoint APM is using - 404 error

I'm using the latest version of the Nodejs APM agent (3.7.0) and running against a trial install of Elastic APM hosted on Elastic. I've configured the agent using both inline configuation (apm.start({})) and environment variables, but I keep getting 404 errors when APM tries to connect.

I'm not sure why this is happening, but I can't tell what URL the APM agent is trying to connect to. I copied the configuration exactly as it appeared in the tutorial. Is there any way to see what endpoint the APM agent is trying to connect to?