getting coverage "unknown" in badges

have been trying to show coverage in code coverage badge. I am getting coverage at CI/CD --> JOBS section but the coverage is not getting updated in gitlab badges.Following is my gitlab-ci.yml file where I am finding the coverage and saving it in artifacts.

variables:
  DOCKER_DRIVER: overlay2
  GIT_CLEAN_FLAGS: -ffdx -e node_modules/
  GIT_DEPTH: 10

stages:
  - test

test:
  image: docker:19.03.12
  services:
    - docker:dind
  stage: test
  script:
    - c8 --all  --reporter=text-summary npm run test 
  artifacts:
    when: always
    paths:
      - coverage

Configuration - Test coverage parsing - "Statements\s+:\s(\d+.?\d+)%"

from getting coverage "unknown" in badges