Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32wl3/STM32WL33/RNG/RNGPCellID0#0x0
RNGPCellID0 register
These bits are read back as 0x0D
https://github.com/modm-io/cmsis-svd-stm32