cannot pull kanaka/emscripten from docker hub

[tarkin000]

I have a bad feeling this is something dumb I'm doing,
but I cannot pull the docker the image.
Things I have tried:
setting the time with ntpdate
reconfiguring tzdata (it threw my clock off by 10min?)
docker pull kanaka/emscripten
sudo docker pull kanaka/emscripten
creating a docker hub account
docker login followed by pull
sudo docker login followed by pull
su to root, docker login, docker pull.

every single time, the downloads finish, but I get 'authentication required'.
I believe my Docker installation is correct- it's from the Jessie repos-
and pulling other images just works:

$ docker pull mono
Using default tag: latest
latest: Pulling from library/mono
5233d9aed181: Already exists 
666418377e5b: Pull complete 
75a87e0601e5: Pull complete 
8e3dafbe502d: Pull complete 
Digest: sha256:32b9d2580388688b8d57742e659f2d021d3d90f036141b1fee81ded64062dd9e
Status: Downloaded newer image for mono:latest

[tarkin000]

Got it sorted.
Looking into debugging dockerd, I turned on debugging
in /etc/docker/daemon.json - which did not exist.
So either setting this to true or creating daemon.json
and restarting - or logging in and restarting- did the trick.