Hi Chao:
It is hard to know the root cause of your issue since I can't reproduce your issue on my side.
From your description, it seems the interrupts is not enabled by FreeRTOS.
If you called FreeRTOS API, but not started the scheduler with function vTaskStartScheduler(), then the interrupts will be disabled. That is done deliberately to prevent interrupt service routines attempting to perform a context switch before the scheduler is running.
There are many LwIP freeRTOS & Baremetal demos under KSDK installation folder, you can refer to it.
Regards
Daniel