How can I completely clear the flash on a BL600 module?

Answer

Open a command prompt window and change directory to where you have unzipped the latest firmware upgrade file. Once you are at the mentioned directory, enter the command: nrfjprog ?eraseall.  This command will completely erase the flash. After the flash is wiped, run the firmware batch file to upgrade the firmware. Once the firmware has been upgraded properly, ensure that the module responds to AT commands. A quick sanity check that the flash is cleared is confirming that the command "AT I 0xC0FE" returns the current license. In this case, there should be no license key since the flash has been erased. Finally, re-enter the AT+LIC command and the module should be behaving as expected.