Question : GitLab pages "project" address

Hi,
I’m using GitLab in my company to host sources ans docs about my projects.

I’ve some 3 docs (Pages) projects, and in one of them, I’ve NO “project” address in the Project > Settings > Pages as :

https://<project>.domain.org 

for this site, only the

http://<user>.domain.org/<project>

How can I ennable this address ? This address is displayed on other projects…

Thanks for your help !