Nginx not responding to port 80 on public IP address

[Adam]

Hi all,

nginx is running and listening on port 80:
        tcp        0      0 0.0.0.0:80              0.0.0.0:*
LISTEN      0          42297      3576/nginx: master
        tcp6       0      0 :::80                   :::*
 LISTEN      0          42298      3576/nginx: master

The server responds fine to requests on port 443, serving traffic exactly
as expected:
        tcp        0      0 0.0.0.0:443             0.0.0.0:*
LISTEN      0          42299      3576/nginx: master

However, it will not respond to traffic on port 80. I have included this
line in my server block to listen to port 80:
        listen 80 default_server;
        listen [::]:80 default_server;

My full config can be seen at https://pastebin.com/VzY4mJpt

I have been testing by sshing to an external machine and trying telnet
my.host.name 80 - which times out, compared to telnet my.host.name 443,
which connects immediately.

The port is open on my router to allow port 80 traffic. This machine is
hosted on my home network, serving personal traffic (services which I use,
but not for general internet use). It does respond to port 80 internally,
if I use the internal ip address (http://192.168.178.43).

I've kind of run out of ideas, so thought I would post here.

Thanks in advance for any support.

Adam
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