Why does the M590 GSM module lose its SIM card?

Question

Atmel AVR

I'm trying to send SMS from the GSM module. The first 10 seconds the network is seen, after that the SIM card is lost and is not restored until the reboot. I feed from the socket (5.20 volts, up to 2 amperes).
I found a SIM card with which the connection is not lost. Its identifier consists of 19 digits. In the rest (which are lost) 18.