Why the Lwip example code cannot run on the my customized board?

Hi,

1. I run the "LwIP_HTTP_Server_Netconn_RTOS" example well on STM32746G-Discovery board. I can see webpage after type "192.168.11.1" in browser.
2. I modified the gpio configuration in "HAL_ETH_MspInit"
3. I modified the HSE_VALUE from 25M to 8M (my board use 8M osc)
4. I try to burn the modified code to our board, but it cannot work and no webpage i can see in browser... i am sure my board has no hardware problem.

Can someone tell any other consideration on the modification to make my board run the example?

Thanks!

Kevin