Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32h5/STM32H523/IWDG/IWDG_KR#0x0
IWDG key register
Key value (write only, read 0x0000)
https://github.com/modm-io/cmsis-svd-stm32