Pipeline KO - Runner - remote: HTTP Basic: Access denied

Recently, the CI pipeline of my Nuxt.js web application (vueJS) hosted on gitlab (private) gives me the error below.

During my last deployment which was a few months ago, everything was going smoothly.

Here for your information is an extract from my .gitlab.ci of my nuxt.js project:

image: node:16

cache:
  paths:
    - node_modules/

stages:
  - stageprod

before_script:
  - "which ssh-agent || ( apt-get update -y && apt-get install openssh-client -y  )"
  - "which rsync || ( apt-get update -y && apt-get install rsync -y )"
  - eval $(ssh-agent -s)

job:deploy_prod:
  stage: stageprod
  only:
    - master
  script:
    - npm install
    - npm run build
    # Inject the remote's private key
    - echo "$SSH_PRIVATE_KEY" | tr -d '\r' | ssh-add - > /dev/null
    - ....

Has there been a recent change in gitlab that is responsible for this error?
Do you know how to authenticate access to gitlab from the runner?