Thanks, this solution worked for me as well.
Blockquote
I have changed
proxy_set_header X-Forwarded-Proto $scheme;
to
proxy_set_header X-Forwarded-Proto https;
I have changed this under / and /ws in location, in the port 80-section strangely enough. I am using https, but these two lines are in the non-ssl section and need to be changed there.
I am running Debian 9 and did a clean install of Zammad 3.1.0 which I later upgraded to 3.2.0. I don’t have any reverse proxies, load balancers or anything. It’s just a ‘default installation’.