Why does SIM7070G have no signal?

Setting NB-IOT or CAT-M is easier to get signal

AT+CMNB=2 //Set NB-IOT mode

AT+CMNB=1 //Set CAT-M mode

AT+CMNB=3 //Set CAT-M and NB-IOT combination mode

Fixed LTE mode can register to the network faster

AT+CNMP=38