Can't get my gitlab pages site working with "www" prefix

Hi, I have created my website with gitlab-pages ans a custom domain, effectivecoding.fr.
I have added the domain effectivecoding.fr in gitlab. The site works well with : effectivecoding.fr, secured with let’s encrypt. :grinning:

Unfortunately, it does not work when I go to www.effectivecoding.fr : I have a 401 Error “- You don’t have permission to access the resource.”

My name server is OVH, and I have followed this documentation : https://docs.gitlab.com/ee/user/project/pages/custom_domains_ssl_tls_certification/#for-both-root-and-subdomains , with this configuration :

I also tried with 2 separate domains in Gitlab : effectivecoding.fr and www.effectivecoding.fr, but the lets’s Encrypt certificate can not be validated for the second domain, and so https is not working.

Do you have any idea?

Thank you in advance,