Yes we did add the folowwing lines that were not in the original configuration to try to make certbot reconize the vhost.
It doesn't work with or without those:
Blockquote
<VirtualHost *:80>
ServerAdmin contact@dragnsurvey.com
ServerName www.dragnsurvey.com
DocumentRoot /path/to/site
<Directory /path/to/site>
Order allow,deny
allow from all
</Directory>
# Les logs (historiques des IPs et des fichiers envoyés)
ErrorLog /var/log/apache2/dragnsurvey.com-error_log
TransferLog /var/log/apache2/dragnsurvey.com-access_log
</VirtualHost>