Please fill out the fields below so we can help you better. Note: you must provide your domain name to get help. Domain names for issued certificates are all made public in Certificate Transparency logs (e.g. crt.sh | example.com), so withholding your domain name here does not increase secrecy, but only makes it harder for us to provide help.
I can login to a root shell on my machine (yes or no, or I don't know): Yes
I'm using a control panel to manage my site (no, or provide the name and version of the control panel): I'm using DirectAdmin
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): I'm using plugin Let's encrypt of Directadmin
I'm a little bit puzzled about what kind of "detailed advice" you expect from us to be honest. Your thread is about the fact your webserver still serves a self signed certificate. But that's to be expected if there hasn't been any Let's Encrypt certificate issued at all. It seems your DirectAdmin Let's Encrypt plugin hasn't worked at all, but without any details about that process, it's impossible to assist you.