Try simply to check what machine has been created (docker-machine ls):
docker-machine ls
Then you can pick one and try your commands with it.
If there is none, you can create one first (docker-machine create).
In the case of the OP:
docker-machine create default
Since the error message was:
Cannot connect to the Docker daemon. Is the docker daemon running on this host?
One of the answers of “Docker command can’t connect to docker daemon” should work:
sudo service docker restart