Hi @gopygrad,
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.