Hi @Nick,
Can you post a video of what you’re seeing from power-on? Ahh, rapid cyan is different!
Rapid Cyan makes me think that your core is missing its keys (the server public key).
Can you try re-flashing the server public key?
dfu-util -d 1d50:607f -a 1 -s 0x00001000 -v -D cloud_public.der
You can grab that key here:
https://s3.amazonaws.com/spark-website/cloud_public.der
Instructions for flashing private keys here: