indeed that was it.
i was specifying the wrong location, forgot that when you run docker-compose up -d command docker mounts certs folder in container according to what we wrote in docker-compose.yml as configuration in the nginx part. so instead of specifying the /etc/certs/fullchain.pem (the one in the container) i was referencing my /etc/rasa/bot_support/certs/fullchain.pem
Last question !! the certificate work only with mozilla ??? @justyn