While loading proxy on BM 3.8 SP5 I get this error for one of the addresses
(reverse proxy on 443)

Searched high & low & the solutions were not working.

Eventually I noticed that the problem might be the fact that the were some
"hanged" connections on port 443 (in tpccon) that could not be deleted

Only way to sort it was to bounce the webserver, which was reverse proxied

That cleared the connections & allowed the proxy to load & bind OK to 443 on
the address in question

If the above is true, maybe it can help somebody else here