ACME_HOSTS on prod env "x509: certificate signed by unknown authority"

[BenWaNH]

Hi,

i'm trying to use Vulcain in my prod stack (no issue in dev with self signed certificate)
So, i'm Docker user and this is my service config in my docker-compose.yml file :

vulcain:
        image: dunglas/vulcain
        environment:
            - ACME_HOSTS=api.example.com
            - UPSTREAM=http://api
        depends_on:
            - api
        deploy:
            labels:
                - traefik.enable=true
                - traefik.tcp.routers.isc-api.rule=HostSNI(`api.example.com`)
                - traefik.tcp.routers.isc-api.entrypoints=websecure
                - traefik.tcp.routers.isc-api.tls=true
                - traefik.tcp.routers.isc-api.tls.passthrough=true
                - traefik.tcp.routers.isc-api.service=service-api-isc
                - traefik.tcp.services.service-api-isc.loadbalancer.server.port=443
        <<: *network

And below, content docker log for Vulcain service:

{"level":"info","ts":1606489658.6425629,"caller":"vulcain/server.go:147","msg":"vulcain started","protocol":"https","addr":""}
2020/11/27 15:09:10 http: TLS handshake error from 10.0.7.11:39992: Get "https://acme-v02.api.letsencrypt.org/directory": x509: certificate signed by unknown authority
2020/11/27 15:09:10 http: TLS handshake error from 10.0.7.11:39990: acme/autocert: missing certificate
2020/11/27 15:09:10 http: TLS handshake error from 10.0.7.11:39996: acme/autocert: missing certificate
2020/11/27 15:09:10 http: TLS handshake error from 10.0.7.11:39998: acme/autocert: missing certificate

For additional informations, i'm using Traefik and Docker Swarm but i don't think that is an impact to this issue

What's wrong with acme config?

Thanks
BenWa