LPC55S69:CMSIS-DAP - ARMv8-M Error

MDK: 5.26.2
SW: SDK_2.6.3_LPCXpresso55S69, rtos_examples/
PACK: NXP.LPC55S69_DFP.12.0.1

compile is ok. When I download, KEIL gives a error

 Build Output:

Cannot access Memory (@ 0x00000000, Write, Acc Size: 4 Byte)
Error: Flash Download failed  -  Target DLL has been cancelled
Flash Load finished at 12:06:27
Load "debug\\freertos_usart.out"
Info: LPC55xx connect srcipt start
Info: APIDR: 0x002A0000
Info: DPIDR: 0x6BA02477
File       : D:\Keil_v5\ARM\PACK\NXP\LPC55S69_DFP\12.0.1\NXP.LPC55S69_DFP.pdsc
Sequence   : DebugPortStart -> EnableDebugMailbox
Context    : Item #0: <block>::Line 29
Expression : "v5\ARM\PACK\NXP\LPC55S69_DFP\12.0.1\NXP.LPC55S69_DFP.pdsc"
E310       : Debug access failed - cannot read AP register 0x08 (AP '2'))

I have tested three computers, all in the same situation. 

What's the problem of these? And how to solve?


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