My setup for https on my Ubuntu server using Nginx with certbot fails with ERR_ADDRESS_UNREACHABLE

My goal is to have Nginx return it’s example welcome page while using https.

I used certbot to create the certificates with the following command:
certbot --nginx -d api.example.com

In my /etc/nginx/conf.d/nginx-example-server.conf
I have the following block:

server {
       listen      443 ssl;
       server_name api.example.com
       ssl_certificate     /etc/letsencrypt/live/api.example.com/cert.pem;
       ssl_certificate_key /etc/letsencrypt/live/api.example.com/privkey.pem;
       include /etc/letsencrypt/options-ssl-nginx.conf;
}

the include /etc/letsencrypt/options-ssl-nginx.conf; includes the following:

ssl_session_cache shared:le_nginx_SSL:1m;
ssl_session_timeout 1440m;
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
ssl_prefer_server_ciphers on;
ssl_ciphers: "<Lots of cyphers>"

ufw status verbose returns:

Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing), disabled (routed)
New profiles: skip

To                         Action      From
--                         ------      ----
443/tcp                    ALLOW IN    Anywhere                   # Open all to access Nginx port 443
80/tcp                     ALLOW IN    Anywhere                   # Open access Nginx port 80
22/tcp                     ALLOW IN    Anywhere                   # Open access OpenSSH port 22
8000                       DENY IN     Anywhere                  
443/tcp (v6)               ALLOW IN    Anywhere (v6)              # Open all to access Nginx port 443
80/tcp (v6)                ALLOW IN    Anywhere (v6)              # Open access Nginx port 80
22/tcp (v6)                ALLOW IN    Anywhere (v6)              # Open access OpenSSH port 22
8000 (v6)                  DENY IN     Anywhere (v6)             
  

If I visit https://api.example.com (not the real url, of course) it responds with ERR_ADDRESS_UNREACHABLE.

/var/log/nginx/access.log and /var/log/nginx/error.log both don’t log anything concerning the ERR_ADDRESS_UNREACHABLE.

I tried to find my ufw log files, but there aren’t any. I tried to find them as described in here: https://serverfault.com/a/516840

I have looked all over for tips and followed a few tutorials. Everything results in the same response. I can succesfully reach the Nginx welcome page over http though.

Help is very welcome! Even if it’s only a better way to debug this thing.