What triggers NGINX .template to copy?

I have set up my site.conf as a site.conf.template file in /etc/nginx/templates/

It has successfully been copied into etc/nginx/conf.d before, but after making some changes to the template and rebuilding the container, it is not copying again. There are no errors in the docker log for the nginx container, in fact it is running (without the sites config).

I have tried changing the local copy of conf.d to 775, but other than that I can't think of what would be stopping it from copying or triggering. Or where to look for error logs. 🙏