Adding a second virtualhost causes apache to crash upon restart

I have a new install of Apache 2.4/PHP 7.4/Postgresql 12 on Ubuntu 20.04LTS.

I am trying to add two virtualhosts. I am following the documentation here https://httpd.apache.org/docs/2.4/vhosts/examples.html

This works for 80, except the second site on 8080 won’t load:

<VirtualHost 45.79.219.72:80>
    ServerName www.example.com
    DocumentRoot "/var/www/html/site/public_html"
</VirtualHost>

<VirtualHost 45.79.219.72:8080>
    ServerName www.example2.com
    DocumentRoot "/var/www/html/site-test/public_html"
</VirtualHost>

If I add the “Listen” lines from the documentation, then apache crashes on restart:

Listen 80
Listen 8080

<VirtualHost 45.79.219.72:80>
    ServerName www.example.com
    DocumentRoot "/var/www/html/site/public_html"
</VirtualHost>

<VirtualHost 45.79.219.72:8080>
    ServerName www.example2.com
    DocumentRoot "/var/www/html/site-test/public_html"
</VirtualHost>

Job for apache2.service failed because the control process exited with
error code. See “systemctl status apache2.service” and “journalctl
-xe” for details.

user1@localhost:~$ systemctl status apache2.service
‚óŹ apache2.service - The Apache HTTP Server
     Loaded: loaded (/lib/systemd/system/apache2.service; enabled; vendor preset: enabled)
     Active: failed (Result: exit-code) since Sun 2021-01-24 16:04:08 UTC; 9s ago
       Docs: https://httpd.apache.org/docs/2.4/
    Process: 98019 ExecStart=/usr/sbin/apachectl start (code=exited, status=1/FAILURE)

Nothing in the error.log.

I’m afraid I have no idea where to start troubleshooting on this.