MC60 Doesn't send any question of AT commands

Hi. I am new at gsm modules. I desgined a dev board for mc60 module. It connects to network and netlight turn on and turns of. I am sending AT or ATI or any command via QCOM V1.6. But mc60 not sending any data. When i changed supply voltage 4V to 3.3V, mc60 sends “UNDER VOLTAGE WARNING”. Why it doesn’t send any AT command answer?

I couldn’t upload photos here they are.

I’ve tried with Putty. There is no problem. QCOM DOESN’T SEND ANY DATA!