Open CPU on MC60

Hi,
i have an MC60 with firmware version MC60ECAR01A09 and I’m trying to load some custom code via the open CPU using an SDK version 1.3. I wrote a simple code that turns an LED on and off, i loaded it onto the module and i noticed that the code i wrote works correctly but the rest no longer works, that is, it seems that the module no longer interprets the AT commands that it they come from the microcontroller and consequently it no longer works. What could be causing the problem?
Thank you

Is it the AT command response nothing?