In case anyone stumbles on this thread while troubleshooting - I had a similar problem more recently and resolved it by opening device.spark.io with port 5683 for TCP, as @kennethlimcp suggested.
In case anyone stumbles on this thread while troubleshooting - I had a similar problem more recently and resolved it by opening device.spark.io with port 5683 for TCP, as @kennethlimcp suggested.