I was installing mailinabox on my self heberged server and the installation stop at the middle :

why did it stop ? how to solve that and reinstall mail-in-a-box without this error ?
Installing nsd (DNS server)…
Generating DNSSEC signing keys…
Installing Postfix (SMTP server)…
Installing Dovecot (IMAP server)…
Creating new user database: /home/user-data/mail/users.sqlite
Installing OpenDKIM/OpenDMARC…
Installing SpamAssassin…
Installing Nginx (web server)…
setup/web.sh: line 30: /etc/nginx/conf.d/ssl.conf: No such file or directory

it appears that Nginx failed to install. Does the server already have Nginx installed? May we know what OS it runs?