STM32F4 + DP83848: Ethernet not working

I am a beginner in electronics. I recently designed a board using the STM32F407VGT6 and DP83848, but after assembly and testing, I encountered a problem.  

The board can be programmed and it runs, but the Ethernet section does not work properly.  

It does not obtain an IP address.  

When I ping any IP address in network range, the Ethernet LED(pin 26) turns on and off, but the Ethernet connection is not actually established.

I would appreciate it if you could guide me regarding the schematic and circuit so I can solve this issue.

• I attach my pcb schematic and board