Why stm32L431cct6 HAL_FLASHEx_Erase give error on power-on Reset?

[AShab.2]

we use stm32L431cct6 in our board and we are using HAL layer.

On power-On reset HAL_FLASHEx_Erase function gives error, but when we reset using RST pin it working fine, can you please suggest how to solve these problem.