"Please add a virtual host for port 80."

Sorry, it turns out that I had put the file at /etc/apache2/virtual.conf instead of at /etc/apache2/other/virtual.conf so it wasn’t being included.

I moved it to the right place, restarted apache again, and then tried

sudo certbot --apache

and now get this:

Saving debug log to /var/log/letsencrypt/letsencrypt.log
Error while running apachectl configtest.

AH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:
Cannot define multiple Listeners on the same IP:port

The apache plugin is not working; there may be problems with your existing configuration.
The error was: MisconfigurationError('Error while running apachectl configtest.\n\nAH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:\nCannot define multiple Listeners on the same IP:port\n')

The main httpd.conf has this section:

<IfDefine SERVER_APP_HAS_DEFAULT_PORTS>
    Listen 8080
</IfDefine>
<IfDefine !SERVER_APP_HAS_DEFAULT_PORTS>
    Listen 80
</IfDefine>

Could that be what is causing the conflict?

I can’t upload my log as a new user, so I have to include it in the post:

2018-10-25 18:59:00,844:DEBUG:certbot.main:certbot version: 0.27.1
2018-10-25 18:59:00,846:DEBUG:certbot.main:Arguments: ['--apache']
2018-10-25 18:59:00,846:DEBUG:certbot.main:Discovered plugins: PluginsRegistry(PluginEntryPoint#apache,PluginEntryPoint#manual,PluginEntryPoint#nginx,PluginEntryPoint#null,PluginEntryPoint#standalone,PluginEntryPoint#webroot)
2018-10-25 18:59:00,905:DEBUG:certbot.log:Root logging level set at 20
2018-10-25 18:59:00,906:INFO:certbot.log:Saving debug log to /var/log/letsencrypt/letsencrypt.log
2018-10-25 18:59:00,908:DEBUG:certbot.plugins.selection:Requested authenticator apache and installer apache
2018-10-25 18:59:01,128:ERROR:certbot.util:Error while running apachectl configtest.

AH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:
Cannot define multiple Listeners on the same IP:port

2018-10-25 18:59:01,129:DEBUG:certbot.plugins.disco:Misconfigured PluginEntryPoint#apache: Error while running apachectl configtest.

AH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:
Cannot define multiple Listeners on the same IP:port
Traceback (most recent call last):
  File "/usr/local/Cellar/certbot/0.27.1/libexec/lib/python3.7/site-packages/certbot_apache/configurator.py", line 2211, in config_test
    util.run_script(self.option("conftest_cmd"))
  File "/usr/local/Cellar/certbot/0.27.1/libexec/lib/python3.7/site-packages/certbot/util.py", line 86, in run_script
    raise errors.SubprocessError(msg)
certbot.errors.SubprocessError: Error while running apachectl configtest.

AH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:
Cannot define multiple Listeners on the same IP:port


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/Cellar/certbot/0.27.1/libexec/lib/python3.7/site-packages/certbot/plugins/disco.py", line 132, in prepare
    self._initialized.prepare()
  File "/usr/local/Cellar/certbot/0.27.1/libexec/lib/python3.7/site-packages/certbot_apache/configurator.py", line 235, in prepare
    self.config_test()
  File "/usr/local/Cellar/certbot/0.27.1/libexec/lib/python3.7/site-packages/certbot_apache/configurator.py", line 2213, in config_test
    raise errors.MisconfigurationError(str(err))
certbot.errors.MisconfigurationError: Error while running apachectl configtest.

AH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:
Cannot define multiple Listeners on the same IP:port

2018-10-25 18:59:01,132:DEBUG:certbot.plugins.selection:Single candidate plugin: * apache
Description: Apache Web Server plugin - Beta
Interfaces: IAuthenticator, IInstaller, IPlugin
Entry point: apache = certbot_apache.entrypoint:ENTRYPOINT
Initialized: <certbot_apache.override_darwin.DarwinConfigurator object at 0x111268a20>
Prep: Error while running apachectl configtest.

AH00526: Syntax error on line 1 of /private/etc/apache2/other/virtual.conf:
Cannot define multiple Listeners on the same IP:port

2018-10-25 18:59:01,133:DEBUG:certbot.plugins.selection:Selected authenticator None and installer None