I recently purchased the RFID/NFC Shield for Arduino and I am having the same problems as a few other people here. I keep getting the "Didn't find PN53x board." message when I try to use the shield. I have tried all the sketches from the Adafruit_PN532 library and the same thing happens. When I reset, the red BUSY light turns off for a second and then stays on continuously and the green PWR light remains on. It is connected to an Arduino Uno R3 using stackable headers. I believe my soldering was fine but I will post some pictures. I may just have a defective board, but please let me know if anything looks wrong. Thank you!