Unable to append certificate TLS Certificate

Traefik Traefik v2 (latest)
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1

I'm trying out the gRPC example in the Docs:

But I'm getting the following error when trying to run Traefik:

/home/ubuntu/traefik# ./traefik --configfile=conf/main.yml --log-level=debug
INFO[0000] Configuration loaded from file: /home/ubuntu/traefik/conf/main.yml
ERRO[2020-03-01T19:08:17Z] Unable to append certificate  to store: unable to generate TLS certificate : tls: failed to find any PEM data in certificate input  tlsStoreName=default

I'm not sure why it's trying to generate a TLS certificate when I'm telling it to use existing ones. Can someone point me in the right direction here? Configs below:

main.yaml

entryPoints:
  websecure:
    address: :4443

serversTransport:
  rootCAs:
    - ./conf/tls.cert

providers:
  file:
    directory: ./conf

api: {}

dynamic.yml

http:
  routers:
    routerTest:
      service: srv-grpc
      rule: Host(`frontend.local`)
  services:
    srv-grpc:
      loadBalancer:
        servers:
        - url: https://localhost:9999
tls:
  certificates:
  - certfile: ./cert/frontend.cert
    keyfile: ./cert/frontend.key