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.
It produced this output: To fix these errors, please make sure that your domain name was entered correctly and the DNS A/AAAA record(s) for that domain contain(s) the right IP address.
My web server is (include version): Ubuntu
The operating system my web server runs on is (include version): Ubunto 20.04
My hosting provider, if applicable, is: Contabo
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 do not know
The version of my client is (e.g. output of certbot --version or certbot-auto --version if you're using Certbot): I do not understand the questions?
You showed two different domains in your opening post.
The first domain (acmcf.fr) has an IPv6 address for the base name.
[LE prefers IPv6 over IPv4 when present and may be part of the problem with obtaining a cert]
And ,for IPv4, it shows: Server: Werkzeug/0.16.1 Python/3.8.5
So it is difficult to tell if it is running Apache or NGINX.
[for IPv6, it fails to connect - again, likely the problem with obtaining a cert for that name]
The second domain (mondomaine.fr - shown in the command line) has one IP for the base name and another IP for the www name.
And they show:
Server: Apache
Server: Apache/2.4.10 (Debian)
So, which is the domain name you are asking for help with?
Then you are likely referring to the domain acmcf.fr only.
I will avoid anything relating to the other domain (mondomaine.fr) from hereon out.
DIG or NSLOOKUP
The problem you are having is likely due to the IPv6 address assigned to the base domain.
If that IPv6 address is not needed, you should remove it from DNS.