Just got off the phone with support, was in the middle of attempting to swap an MX84 for an MX250 (our AutoVPN hub). Everything went smoothly until it came time for the MX250 to check in with the dashboard. Gave it probably half an hour to check in, it never did.
Verified I can ping it from our internal network, verified the switchport it's connected to is seeing a bit of traffic in/out. Verified arp entries, etc.
Support tried a couple things like removing the MX250 from the hub network, adding it back. They verified that they can see it talking to the dashboard, and the dashboard talking back. Dug around a little, turns out there's a known bug right now preventing new devices from checking in with the dashboard.
Anyone else heard about this?
Edit: a few more details