docker-compose example not working behind nginx proxy

So I downloaded both the example docker-compose (changed port to 5010 for exposed port) and added proxy to nginx.
I also downloaded db.env

When I run `docker-compose up` it appears to start but when I browse to my domain which forwards to localhost:5010 i get a 502 gateway error.

I do not see what the issue is, can someone help?

http://sprunge.us/q2JKN9

Start by reproducing the setup with the example docker-compose configuration, db.env, port 5010, and the reported nginx proxy. Check the docker-compose startup output and nginx proxy behavior; done means the Matomo site loads through the domain without a 502 response.

Written by the indexing model from the issue text.