Cut and paste this URL to share the unmodified register and value:
https://regviz.com/r/stm32/stm32l5/STM32L552/FLASH/ACR#0x0
Access control register
Latency
Flash Power-down mode during Low-power run mode
Flash Power-down mode during Low-power sleep mode
LVEN
https://github.com/modm-io/cmsis-svd-stm32