MFRC522 issue with Pico

I've upgraded my pico to the latest firmware 2.01, and testing the MFRC522 NFC/RFID module that came with the kickstarter geek kit. I've tried running the test code on this page and another and finding I'm getting some kind of runtime error.

Uncaught Error: MFRC522 Request Error 254
 at line 1 col 189
...("MFRC522 Request Error "+a);a=this.r(20);return this.ra(18,...
                              ^
in function "req" called from line 1 col 34
this.w(26,7);return 0<this.req(38).length
                                 ^
in function "isNewCard" called from line 1 col 16
this.isNewCard()&&a(this.getCardSerial()­)
               ^
in function "findCards" called from line 6 col 3
 });
  ^
in function called from system

I'm running this test code

SPI1.setup({sck:B3, miso:B4, mosi:B5 });
var nfc = require("MFRC522").connect(SPI1, B1/*CS*/);
setInterval(function() {
 nfc.findCards(function(card) {
  print("Found card");
 });
}, 1000);

I wonder if anyone else has come across this issue?

Thanks
Michael.