You'd have to find the docker container id and exec into it first.
docker ps
docker exec -it <container_id> /bin/sh
See if you can't look at the logs using this:
https://docs.start9.com/latest/user-manual/managing-services#service-logs
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Recurring errors on the log...
ERROR: CLWebSocket => Web socket error: connect ECONNREFUSED 178.18.0.3:3001 ERROR: WebSocketServer => Broadcasting error to clients...: {"error":"connect ECONNREFUSED 178.18.0.3:3001"}.
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-bash: lightning-cli command not found