Two identical services: agent 6.0.0.154 never registers with New Relic in a network with no default route (proxy only), while 5.24.0.153 works with HTTPS_PROXY. Giving the v6 service a direct route makes it register, so the agent is ignoring the proxy.
New Relic Python agent ignores HTTPS_PROXY (use NEW_RELIC_PROXY_HOST)
The Python agent does not read the standard HTTPSPROXY env var; it uses its own NEWRELICPROXYHOST (plus NEWRELICPROXYPORT and related NEWRELICPROXY* settings). Setting NEWRELICPROXYHOST=$httpsproxy resolved the reporter's registration failure immediately. Same issue also caused an unrelated-looking httpx instrumentation crash ('NoneType' object has no attribute 'process_response'), which was fixed in the following agent release.
Source: https://github.com/newrelic/newrelic-python-agent/issues/128
Source: https://github.com/newrelic/newrelic-python-agent/issues/128