Arduino RFID with the Arduino UNO, Ethernet Shield and RC522

michel_kempf:
Is something in Code wrong?

How are we to know? You are the one with the code. You are the one with the hardware. You are the one with the serial output, that you haven't shared. You are the one that can see what is happening, that you haven't shared.

"It doesn't work" gets you nothing but insincere sympathy. "It does this..." while I expect it to "whatever..." gets you answers.