BlinkUp Fixture - production code not deploying

I’m writing fixture code to run on an impFactory appliance.
When I blinkup an imp006 in the test zone it successfully downloads and runs the DUT code and blesses the device. The blinkup status is logged and forwarded back to the fixture correctly.
The device is then assigned automatically to my test-zone production group as I’d expect.
However the production group is set to “deploy immediately after blessing”, but this isn’t happening.
The agent is “Unenrolled” and there is no “Last enrolled” info.
Any ideas what I might be doing wrong?
Thanks,
Tony

My bad - just discovered the documentation on factory activation!
https://developer.electricimp.com/manufacturing/factoryactivation