gitlab pages ci file needs pages:true

the gitlab ci/cd file (.gitlab-ci.yml) for gitlabpages needs pages:true to generate your project-HASH.gitlab.io site

dpl:
  stage: deploy
  pages: true

this will appear as a magic step in your deploy pipeline

deploy
  dpl
  pages:deploy

https://docs.gitlab.com/user/project/pages/#using-gitlab-pages