System Workbench for STM32

STM32L476 Nucleo board frequency selection

It will appear that your SystemClock_Config function with these PLL parameters does not match the System Clock of the STM32L4xx family.
What version of CubeMX do you use?

The L4 operate at the SYSCLK max frequency of 80MHz.
PLL / M = 16 and PLL configurations N = 336 are not allowed.
The maximum permissible values are PLL / M = 8 and PPL N = 86.
Please review the Reference Manual or into CubeMX Clock Configurator Tab.

I think that your function is more like that of a family STM32F4 or F7 and in these conditions

Oscillator Source HSI (which is the internal Oscillator 16MHz)
One would get for a F4 or F7.
SYSCLK (Hz) = HSI / M * N / P = 16000000/16 * 336 / 2 = 84MHz