Do you Know what ? I had reboot the vps, then httpd. Then it did not work : I mean from client side I had error something like ssl_something_too_long. Ok. So turn around this and finally I had an other error. I checked SSL Server Test: www.nuage.dennet.eu (Powered by Qualys SSL Labs) which say
No secure protocols supported
And they explain in this case
if you get this message, but you know that the site supports SSL, wait until the cache expires on its own, then try again, making sure the hostname you enter uses the "www" prefix
Right, I waited, no changes, of course. But then, certbot had set up a file ssl.conf, that include these parameters :
SSLProtocol all -SSLv3 SSLProxyProtocol all -SSLv3
So I activated that ssl.conf file. Since then I have again the first error I had :
SSLCertificateFile: file '/etc/letsencrypt/live/www.nuage.dennet.eu/fullchain.pem' does not exist or is empty
The behaviour, don't know if it's from httpd or openssl part, is not stable isn't it ? There might be a bug somewhere no ?
Just to mantion that I have read also Unable to establish SSL connection: wrong version number
He also have a problem of version... but finally have to deal with a "default server" (I do not understand everything I should say). But for me the error reporting of ssl is messy. In fact you do not get the error code of the problem you are facing, and more than that for given config files in http you could have something working... one day... and not working after simple reboot.