Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32u5/STM32U575/FLASH/FLASH_PDKEY2R#0x0
FLASH bank 2 power-down key register
Bank 2 power-down key
https://github.com/modm-io/cmsis-svd-stm32