visualdensity,
Thanks for reporting the issue! The flashing magenta light means that your Core successfully connected to our servers, and was in the middle of auto-updating. The solid magenta light means that it dropped a packet during the update process, so it got stuck. We’re working to improve the reliability of the over-the-air updates so that this happens less frequently.
In order to resolve the issue, make sure you’re in good range of Wi-Fi, and press the “RST” reset button on the Core. With the USB power facing away from you, it’s the button on the right. Tapping it once should cause the Core to reconnect to your network and begin the auto-update process again. Try this a few times if it’s still having trouble completing the update. If you’re still having issues, be sure to let us know, and we can help you debug further.
Will @ Spark