I've been running tests with MQTT with the board. It was hung in the 'ready loop' (checking ready and return is always 0). I pressed the reset button to restart and now it won't enumerate on the USB and pressing the reset button twice and nothing. The load led never lights up, only the power led. Was running with a battery and connected to USB for debut messages. It appears that it's useless now. Anyone have any ideas as to whether there's any recovery? I've disconnected the battery and USB and let it set without any power for a while but still won't work when connected.
and pressing the reset button twice and nothing.
You need to press the reset button twice pretty quickly. Did you do that?
After that, the "L" LED should start pulsing. If it doesn't, best case scenario is that the bootloader was somehow corrupted. Worse case scenario is that the hardware was damaged.
I did try that but now have egg on my face. Evidently something with the USB driver/hardware on my Linux Mint PC. I shut it down (powered off) and when powered back on the MKR1500 is back alive. Don't know why I didn't think of that sooner instead of later. Thanks for the reply. Recently I had a program loaded that caused similar symptoms and I was so happy to find out about pressing the reset button twice quickly. Off and on I've had problems on this PC with the 1500 USB enumerating but in those cases I'd try another USB port and it would start working. That had failed this time. Anyway if anyone is on Linux and has this symptom they might try shutting down and restarting Linux.
We are glad that you are able to resolve the issue.
Why we do double-tap on the mkr 1500 boards?
Quickly double-tapping the reset button will usually put the board into the bootloader mode. Once it is in bootloader mode it will be recognized as a com port and you should be able to use Tools > Burn Bootloader to restore the board.