OK I think I found my error.. I had made a back-up copy of the config file in the same directory, sites-enabled, instead of putting it in sites-available (or anywhere else!).. so nginx was no doubt reading both config files. Deleting (or moving instead, no doubt) the back-up file helped and it also stopped the “nginx: [warn] conflicting server name "" on 0.0.0.0:80, ignored” error message.
On my lan, alarmdecorder / nginx is on 192.168.1.98
https://192.168.1.98/keypad/ works fine on Chrome
however
https://192.168.1.98 resolves to
http://alarmdecoder-demo/keypad/ and fails (Error code: ERR_NAME_NOT_RESOLVED)
I can live with that however I feel like it is a serviceable configuration but still has issues well beyond my knowledge level of nginx.
On IE,
https://192.168.1.98/keypad/ resolves to
http://alarmdecoder-demo/login?next=%2Fkeypad%2F and fails (still using the first config file you suggested) Can test the new config file if you like but I am good with the suggestion to ditch IE.. which I never use unless testing.