Hi,
The IP register is not set correctly, the priority number must be written to the 7-4 bits of the register.
S32_NVIC->IP[33] = 0x30; // Priority level 3
See Chapter 7.2.1 of the RM.
But this should not cause any problems.
Did you enable interrupts in LPUART CTRL register?
Is the name of the interrupt handler function correct?
As per S32K144.h, it is
void LPUART1_RxTx_IRQHandler(void)
Regards,
Daniel