Update cnMaestro IPv4 management URL to FQDN

I have been trying to update our on-prem cnMaestro management URL to use an FQDN with a signed cert.
The cert has uploaded and the login page loads on the resolved FQDN without errors or warnings.
I have updated the server-name in /etc/nginx/conf.d/default.conf to the FQDN
I can see the requests being successfully processed in the nginx logs but I cannot get past the login page. I suspect it’s a routing issue in the application but I can’t see where or how to resolve.

Any help appreciated