Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32u5/STM32U535/FLASH/FLASH_OEM2KEYR1#0x0
FLASH OEM2 key register 1
OEM2 least significant bytes key
https://github.com/modm-io/cmsis-svd-stm32