Wildcard certificate does not work

Traefik Traefik v3 (latest)
12

Maybe try switching around:

      - "traefik.http.routers.wildcard_cert.tls.domains[0].main=sub.example.com"
      - "traefik.http.routers.wildcard_cert.tls.domains[0].sans=*.sub.example.com"
      - "traefik.http.routers.wildcard_cert.tls.domains[1].main=example.com"
      - "traefik.http.routers.wildcard_cert.tls.domains[1].sans=*.example.com"

Or try (related post)

      - "traefik.http.routers.wildcard_cert.tls.domains[0].main=example.com"
      - "traefik.http.routers.wildcard_cert.tls.domains[0].sans=*.example.com,*.sub.example.com"

Make sure domain or zone sub. os registered with your DND provider.