Im using Jlink Edu Segger, one time i saw unsecuring option, i chose to unsecure, i think it did nothing, becouse im still geting the same error, This board is K60 Mini Board from mcuzone.com, i checked that oscilator works, its okay. When i try using jflash arm 4,70 to erase, it looks:
Jlink foun 1jtag device Core id 0x4BA00477 Cortex M4
-reading cfi info
-could not find cfi compilant flash device
-detecting flash memory
-ERROR: Could not find any flash devices
-ERROR: Failed to connect
Still no idea to fix it. This board had demo firmware for present usb mass storage, and it worked.