I got the same issue. Proxy behind a proxy.
The problem is the HAProxy of openbalena use HTTP on port 80 and TCP on port 443. So the first proxy has to listen on TCP for the port 443 too. But in almost all cases, 443 is already used for HTTPS. https://github.com/balena-io/open-balena/blob/master/haproxy/haproxy.cfg
I cannot change my configuration so I will try to figure out how to change openbalena’s ports.