Mini W5100 Ethernet card & MEGA 2560

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I connected my Mini W5100 FTCBlock card to an Arduino NANO and used the DHCPAddressPrinter example sketch from the Arduino library. I got it working great in minutes. However, my project grew beyond the NANO, so I had to switch to an Arduino MEGA2560. A week later and countless hours of watching You Tube tutorials and reading many technical specs and articles and it still will not work. I have a Ethernet shield that I can connect to the MEGA2560 and it works well. The end game is to use a MEGA 2560 PRO and the Mini W5100 so the interconnections are soldered wires. I want to avoid mechanical connections for vibration and corrosion reasons.

What is the deal with the compatibility between these boards? I have tried every possible interconnection twice. I have put in delays to allow time for connectivity. I have pinMode 53 to OUTPUT and even digitalWrite it LOW and still no communication. Is there a special library?

I could really use some help.....

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The W5100 uses the SPI bus. If you check the "Connections" table in the SPI library documentation:

You can see that on the Uno (and thus Nano since they use the same pin mapping), the SPI pins are 10-13. On the Mega the SPI pins are 50-53. For this reason, if you try to connect an SPI device to pins 11-13 on the Mega it won't work.

So how is it possible that a W5100 shield works on both an Uno and a Mega when that shield doesn't even connect to the header that contains pins 50-53? The answer is that the SPI pins are also broken out on the ICSP header. That header is located in the same place on the Uno, Mega, and Leonardo (which also doesn't have SPI on 10-13). So a shield only needs to use the ICSP pins for the SPI bus connection to work universally on all these boards.