All Spark Cores can't connect to the cloud

Troubleshooting
7

This could be due to some issues with DNS resolution on the Cores after a server switch.

Try running these commands after clearing the WiFi credentials and putting your device in DFU Mode

particle flash --usb cc3000
particle flash --usb tinker
particle keys server
particle keys doctor <youDeviceID>

And then in Listening Mode reapply the WiFi credentials

particle serial wifi