I recently updated the firmware succesfully. This is my story:
I have a SODAQ NB-iot shield (sara-n211 02b-00) and Crowduino M0 SD.
It was on firmware B656 (and did not respond to AT commands like ATI9 and AT+NCONFIG="CR_0859_SI_AVOID","FALSE").
Uploaded nbIOT_serial_passthrough sketch with commented line #define R4XX
updated with sara-N211-02X-01.fwpkg
Now it does respond to AT commands like ATI9 and AT+NCONFIG="CR_0859_SI_AVOID","FALSE".
Next, connect the board to orange.allthingstalk.com with belgian NB-iot simcard. Anyone out here who can give me some info?