@cwharp, did you ever get a resolution on this?
I am having the same issue. Opened support ticket #122581, but haven’t heard anything after the canned troubleshooting and request for a video of the issue.
I did grab a packet capture, since I can reproduce this on demand. I can see traffic from the Data Center all the time. During the Core boot sequence, I see it pull an IP address and connect to some AWS services. Then the traffic stops when the core shuts down.
I wonder if attaching that packet capture was a good thing or if it just confuses the matter. I am sure they can see the details in their AWS console.
I did notice that the data center publishes it’s GPS data, so at least I got a stratum 1 time source out of it 
Anyway, just curious how things turned out for you while I sit and wait.