I have two Spark Cores. The first connects on the network fine. It has the slowly fading in and out blue main LED.
The second starts with the D7 LED on as a faint? blue. The main LED never lights, no matter what I do. The D7 LED never changes, never goes out. I have done the factory reset using the two buttons.
Both of these have the chip antenna. I’ve checked and both have the white bar near the top.
I have powered off the bad one and powered it on, while holding down the left button (the mode button).
I have switched the USB cables between the two units. The good one reboots and continues to run. The bad one still has the single D7 LED on but the main LED stays off.
I do not, at this time, have a JTAG interface.