Failed authorization procedure. The client lacks sufficient authorization

OK, let’s have a look at this file:
cat /etc/apache2/sites-enabled/hypnosejoaillerie.com.conf

<VirtualHost *:80>
ServerAdmin carlo@mennellablog.info
ServerName hypnosejoaillerie.com
ServerAlias www.hypnosejoaillerie.com
DocumentRoot /var/www/hypnosejoaillerie.com/public_html
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
RewriteEngine on
RewriteCond %{SERVER_NAME} =www.hypnosejoaillerie.com [OR]
RewriteCond %{SERVER_NAME} =hypnosejoaillerie.com
RewriteRule ^ https://%{SERVER_NAME}%{REQUEST_URI} [END,NE,R=permanent]

just as further information:
bussolarte.it and hypnosejoaillerie.it have same record A pointing to the same VPS IP (5.189.131.41).

by typing https://www.hypnosejoaillerie.it/ the SSL certificate belongs to bussolarte and the invalid certificate is shown.

Try restarting Apache web server.
It should be serving the redirection (not the 403)

hmm...
Unless maybe there is something "protected" about the document root directory?

I restarted it many times.
No the whole /var/www has chmod -R 755 and chown -r www-data

it is not the first virtual host I configured with a Let’s Encrypt certificate, as you can see from the details above.

Let’s be sure we are on the right system.
Please show output of:
curl ifconfig.me

Schermata 2020-09-19 alle 23.19.33

Ok we ARE on the right system.
I don’t know what has happened…
Your HTTP and now HTTPS are not being served correctly for that domain.
See: https://www.ssllabs.com/ssltest/analyze.html?d=www.hypnosejoaillerie.it

It seems there is something confusing apache and it doesn’t properly match the names and then serves the defaults for both.
This may be due to “hidden” characters in the config (that can’t be displayed - so you can’t even see them)
Or other reasons.
I would rule that out by retyping the vhost configs over by hand.
[at least start with the lines that have ServerName and ServerAlias - delete and retype them in]

HAHAHAHA!!!!!
The problem has been there all along!
We (at least I have) hyper-focused on the spelling of "hypnosejoaillerie".
But the problem is NOT there.
It is right next to that:

One is ".IT" and the other is ".COM"

Your server has NO vhost config covering the .IT name, so it is forced to serve up the default config.

I have bot domain .com and .it
The virtual host hypnosejoaillerie.com is the one where is hosted the whole site, hypnosejoaillerie.it was suppose to be a redirect to it, but I’m facing problem to get the SSL certificate.

Redirection?
The name clearly resolves to this IP.
This IP has no vhost config to cover that name.

There are both virtual hosts configured

Then you are not using the second one.
Only one is being used:
[look at the output of apachectl -S above]

*:80 is a NameVirtualHost
port 80 namevhost vmi404536.contaboserver.net (/etc/apache2/sites-enabled/000-default.conf:1)

port 80 namevhost bussolarte.it (/etc/apache2/sites-enabled/bussolarte.it.conf:1)
alias www.bussolarte.it

port 80 namevhost hypnosejoaillerie.com (/etc/apache2/sites-enabled/hypnosejoaillerie.com.conf:1)
alias www.hypnosejoaillerie.com

port 80 namevhost mennella.blog (/etc/apache2/sites-enabled/mennella.blog.conf:1)
alias www.mennella.blog

port 80 namevhost mennellablog.info (/etc/apache2/sites-enabled/mennellablog.info.conf:1)
alias www.mennellablog.info

port 80 namevhost mennella.blog (/etc/apache2/sites-enabled/roundcube.conf:1)

port 80 namevhost webstorecorallo.it (/etc/apache2/sites-enabled/webstorecorallo.it.conf:1)
alias www.webstorecorallo.it

There is no ACTIVE vhost config for “www.hypnosejoaillerie.it”.

OK?!
And which one has the name “www.hypnosejoaillerie.it” in it?

grep -Ri 'www.hypnosejoaillerie.it' /etc/apache2

I do see the one with the name “www.hypnosejoaillerie.COM” in it.

Then show the output of this again:
sudo apachectl -S

OR [cut to the chase]:
sudo apachectl -S | grep -i hypnosejoaillerie

reduce the clutter:
sudo apachectl -S | grep -i hypnosejoaillerie