I am having Ethernet troubles. I made a PCB that has Ethernet. It pretty much mirrors what is on the stm32 nucleo boards, with the exception that it uses a magjack. When I plug in a standard Ethernet cable, it works fine. When I try a flat one, it does not work and I cannot communicate. I plug the flat cable into a computer to a router or something, it works fine, though. Is there something specific to flat Ethernet cables that make it different?