Test connection opens the installer.php within the results div

That is quite odd. Sounds like a config setting with Nginx needs to be adjusted. Have you tried to contact your server admin for some clues?

Unfortunately I am the server admin in this case. I set up the server using Easy Engine and in the past I’ve used duplicator to move sites onto a similar environment no problem. To me the Nginx conf looks okay. Any ideas where a problem might be in the configuration?

Either way thanks very much for making such a great plugin!

Have you tried another browser to validate that it is indeed the Nginx setup? My only thought at the moment is maybe try and force the installer.php to clear its cache headers with something like this:
https://stackoverflow.com/questions/1037249/how-to-clear-browser-cache-with-php

I ‘m not sure to be honest…