Hi JACK LIU
Thanks for your updated information, I checked your MKW36Z512XXX4 has:
• 256 KB program flash memory plus 256 KB FlexNVM on KW36Z
• 8 KB FlexRAM supporting EEPROM emulation on KW36Z

So, the FlexNVM area should can be read.
Do you use the SDK code which can be downloaded from this link:
Welcome | MCUXpresso SDK Builder
Use the flash code to read the related FlexNVM instead of the IAR directly, whethet that method works or not?
If you suspect the flash project, you can check the related protect address, any protection on your side?

BTW, in the future, if you have any KW questions, you can create the question in this community:
Wireless Connectivity
If you still have questions about it, please kindly let me know.
Kerry
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