Following the new information you provided on Semanage errors Could it be that you have some firewall running?
Are you able to access passbolt from the server? If you execute the following commands what is the output?
curl -ilkvv -H "Host: your_fullbaseurl_hostname" http://your_passbolt_ip_or_domain
or just
curl -ilkvv http://your_passbolt_ip_or_domain
Are you forcing SSL from passbolt? If you do, do you have the nginx ssl enabled configuration in place and the SSL certificates?
Are ports 80 and or 443 open in the server? Could you check that you can access those ports from the client?