I suspect you're missing authorization. When you connection attempt is made, your Shield should ask to allow developer connection. If it doesn't do it, plug-in will not be able to communicate and will be "offline".
Also, I do not know if Shield will allow multiple developer connections. If you've moved from another device/ip address, maybe go into Shield set up and disable current authorization in developer options.
If it all fails, PM the log to me, I'll see what I can find.