Hi, I am using a server running WHM and I have enabled Auto SSL to use Let's encrypt. Everything was working great. I went into one of the Cpanels on this VPS server and ran the Auto SSL for the site, no issues.
Now that I have enabled Varnish Cache I cannot get the auto SSL to work and I get a 404 on acme-challenge.
I read about using Nginx as a reverse proxy and have installed Nginx this morning. I looked at some tutorials on configuring Nginx to work with lets encrypt. But they all talk about installing the certificates from the command line and then setting the configuration file in Nginx to use reverse proxy.
Welcome to Let's Encrypt forum!
I haven't use cPanel in a while so I did some research on how Vanish works with cPanel. Unfortunately, I don't think I could help you with this because cPanel didn't officially support Vanish. Link: https://forums.cpanel.net/threads/easyapache-4-varnish-ssl.676445/.
Because cPanel developed AutoSSL, so if they do not integrate Vanish with their EasyApache (or the newer software names) there might be some issues that need specifc diagnosis from their devs.
If you (and your clients) are using Cloudflare, you might want to consider using their "Origin SSL".
Beside Let's Encrypt, you can also use cPanel's AutoSSL CA, which might offer you more validation options.