ERR_NGROK_SHIP_PUBLISH_TARGET_DOCKER_HUB_REPOSITORY_REFUSED: Docker Hub refused to create repository REPOSITORY (HTTP STATUS) - ngrok documentation

What does ERR_NGROK_SHIP_PUBLISH_TARGET_DOCKER_HUB_REPOSITORY_REFUSED mean?

ngrok returns ERR_NGROK_SHIP_PUBLISH_TARGET_DOCKER_HUB_REPOSITORY_REFUSED with this message:

Docker Hub refused to create repository <REPOSITORY> (HTTP <STATUS>). Check that the push credential can write to namespace <NAMESPACE>.

Where can I get more help with ERR_NGROK_SHIP_PUBLISH_TARGET_DOCKER_HUB_REPOSITORY_REFUSED?

Email support@ngrok.com and include the error code.