Arduino atmega2560 with wiznet850

I have two costume boards based on Arduino mega2560 with wiznet850 ethernet module to send UDP packet over ethernet. one of them has atmega2560 16u-TW and the other one has atmega2560 16u-TH .

I checked the hardware connection for both boards and everything is working.

the issuse is that the first board (with atmega2560 16u-TW) is just working fine, meaning it takes an ip and i can ping it from my pc locally. however; the one with (atmega2560 16u-TH)can not take an ip ( it shows me that ip is 0.0.0.0 and sometimes 255.255.255.255).

doese anyone faced the same problem on know why this happens?

is the MAC address different?

Did you try swapping Ethernet modules?

yes I am sure they are different

yes, i did swap the modules and i get the same issue

do you think (TH) and (TW) would be the reason for this issue?