EC200A sometimes cannot reach internet for days (QMTOPEN: 0,3) even after reboot

IoT Modules LTE Standard Module
1

Module: Quectel EC200A
Firmware: EC200AEUHAR01A24M16
Host MCU: STM32
Operator: MAGTICOM (Georgia)
Protocol: MQTT over SSL (port 8883)

Problem description

We have multiple deployed devices using EC200A that connect to an MQTT server.

Sometimes the device cannot connect to the internet and MQTT fails with:

+QMTOPEN: 0,3

The strange part is:

  • Sometimes the device works perfectly for weeks
  • Sometimes it cannot reach the internet for hours or even days
  • Then suddenly it starts working again without any change

We have already tested:

  • different EC200A modules
  • different SIM cards
  • full power cycle of the device

The problem still occurs randomly .

Typical diagnostics when the problem occurs

AT+CEREG?
+CEREG: 0,0

AT+CGATT?
+CGATT: 0

AT+QNWINFO
+QNWINFO: "HSDPA","28202","WCDMA 900",3087

AT+CSQ
+CSQ: 15,99

AT+COPS?
+COPS: 0,0,"MAGTICOM",6

Signal strength looks acceptable.

After some time (sometimes minutes, sometimes much longer) the module finally registers to the packet network and MQTT works normally.

MQTT configuration

ATE0
AT+CGDCONT=1,"IP","internet"

AT+QMTCFG="recv/mode",0,0,1
AT+QMTCFG="SSL",0,1,2
AT+QSSLCFG="seclevel",2,1
AT+QSSLCFG="sslversion",2,4
AT+QSSLCFG="cacert",2,"cacert.pem"
AT+QSSLCFG="ignorelocaltime",2,1
AT+QSSLCFG="ciphersuite",2,0xFFFF
AT+QSSLCFG="sni",2,1

Connection:

AT+QMTOPEN=0,"v1c829ee.ala.eu-central-1.emqxsl.com",8883
AT+QMTCONN=0,"client","user","pass"

Questions

  1. Is it normal for EC200A to stay in CEREG: 0,0 for long periods?
  2. Should the application always wait for +CEREG: 1 before activating PDP?
  3. Could this be related to network scanning between LTE and WCDMA?
  4. Are there recommended AT settings for more stable network attachment?

Any advice or recommended initialization sequence would be greatly appreciated.

2

Dear Customer,

Thank you for reaching us. Please find answers to your questions below.

Q1) Is it normal for EC200A to stay in CEREG: 0,0 for long periods?

No. Short periods are normal, but hours/days = abnormal and usually caused by:

  • RAT/PLMN scan oscillation (LTE ↔ WCDMA)
  • Network barring after repeated failed attach attempts
  • Wrong RAT/band configuration
  • Weak/marginal RF area

Minimal diagnostics to enable:
AT+CEREG=2

AT+CREG=2

AT+CPIN?

AT+CFUN?

AT+QENG=“servingcell”

AT+QENG=“neighbourcell”

Q2) Should the application wait for +CEREG: 1 before activating PDP?

Yes. Always.
Correct sequence:

  1. Wait for: +CEREG: 1 (home) or 5 (roaming)
  2. Confirm: +CGATT: 1
  3. Then activate PDP and start MQTT/TLS

Starting PDP before registration → long delays + backoff timers.

Q3) Could it be caused by LTE/WCDMA scanning?

Very likely.
Mixed-coverage areas cause the EC200A to jump between RATs and stay unregistered for long periods.

Fix:
Lock or prefer the strongest RAT (often WCDMA‑only for Magticom 900 MHz).

Q4) Recommended AT settings for stable attachment

Core configuration:

AT+QCFG=“nwscanmode”,2 ; WCDMA only (or lock LTE if LTE is stronger)
AT+QPSMS=0 ; disable PSM
AT+CEDRXS=0 ; disable eDRX
AT+CEREG=2 ; enable URCs

If not registered in ~2 minutes:

AT+CFUN=0
AT+CFUN=1

If still stuck:
AT+CFUN=1,1 ; full reboot