Did you use
letsencrypt-auto with the apache plugin, i.e. did the client setup the certificates in your web server, or did you do that manually?
If you used the apache plugin, you can likely use the
./letsencrypt-auto rollback command to undo the configuration changes that enabled SSL. (You’ll obviously also have to make sure to only link to the
http:// version of your site everywhere.)
If you manually changed your web server configuration to enable SSL/TLS, you’ll have to undo those changes manually as well. This probably involves removing the SSL
<VirtualHost>. Happy to help if you provide your configuration files, or in case we can help you with fixing the issues that are causing you to drop SSL!
To clarify what revocation is about, that’s basically a way for you to tell the CA (Let’s Encrypt) and browsers that the certificate you obtained for your site is not to be trusted anymore, for example because the private key was stolen. It’s not a way to uninstall or disable SSL in your web server.