Failed to request job: runner requestConcurrency

in my gitlab CI UI log I'm seeing this output and it get's stuck there for 2hrs:

Pulling docker image registry.gitlab.com/...

when running my gitlab runner with autoscale docker+machine with digitalocean I'm getting this inside the log output

Failed to request job: runner requestConcurrency meet  builds=1 runner=6e8adb7b

What does this mean, how to resolve? Current conf file is:

[[runners]]
  name = "ttg6"
  url = "https://gitlab.com/ci"
  token = "..."
  executor = "docker+machine"
  limit = 24
  environment = ["DBUS_SESSION_BUS_ADDRESS=/dev/null"]
  [runners.docker]
    host = "unix:///var/run/docker.sock"
    hostname = "..."
    image = "python:2.7"
    postgres = "9.3"
    # allowed_images = []
    privileged = true
    # environment = [ "DOCKER_DRIVER=aufs" ]
  [runners.machine]
    IdleCount = 0                   # There must be 5 machines in Idle state
    IdleTime = 300                  # Each machine can be in Idle state up to 600 seconds (after this it will be removed)
    MaxBuilds = 100                 # Each machine can handle up to 100 builds in a row (after this it will be removed)
    MachineName = "auto-scale-%s"   # Each machine will have a unique name ('%s' is required)
    MachineDriver = "digitalocean"  # Docker Machine is using the 'digitalocean' driver

what am I missing? it used to work until a few days ago and now stopped. I'm using gitlab.com