alzhao
2
This only happens to one modem, right? The other modem is working OK?
Can you reset the modem? Also try to lock the modem in 4G or 3G mode so that it does not roam to 2G.
AT command to lock to 4G LTE
AT+QCFG="nwscanmode",3,1
AT command to lock to go back to auto
AT+QCFG="nwscanmode",0,1