GL-X750 V2 and AT&T Stuck on 3G with NOCONN state

I just bought my GL-X750 V2 Router from amazon the other day with high hopes for it, as it was said to be an “AT&T Verified Router”. With the AT&T SIM card installed today, the router is locked in 3G with a “NOCONN” state, not sure what to do about this anymore.

I have already taken the following actions:

  • Upgrade firmware to 3.203, latest fix for recent AT&T problem listed in this GL-Inet Forum Post.
  • Try different APN’s, such as broadband, phone, etc.

My current AT&T Plan is a tablet plan, has there been any need to specifically use a prepaid SIM?

Maybe the tablet plan SIM locks some IMEI. X750V2 is identified as IOT devices, not tablet.

But you can try all the apn here North American Carriers, ATT, Verizon, Cricket, T-Mobile Setup and Update 2021

Be sure to set ttl to 65 in the settings.

Use ttyUSB3 as device, not cdc-wdm0

Try lock band, find out which band AT&T is using and lock that band using AT command.

Maybe the tablet plan SIM locks some IMEI. X750V2 is identified as IOT devices, not tablet.

This could be the case. Our previous router, the RUT240, seems to have worked fine on this same plan, but I’m not sure if it’s registered with AT&T as an IoT device.

I did try all of those settings just now with no luck. I should add that when I tried locking the router to only 4G, the “3G” symbol went away, and the SIM went to an “unregistered” state again. When in 3G though, the connection state is NOCONN

What’s the likelihood this is caused by having the wrong data plan?

NOCONN is a normal state that indicates that the network has been registered. In LTE mode, you can try different APNs first.
Also, can the information returned by Cells INFO be shared?

@luochongjun Here is the Cells INFO:

Neighbourcell data Click Here

I tried locking the router into 4G Mode, and all Cells Info disappeared, with no neighbourcell or servingcell info available at all. At this point, the SIM card was also no longer registered.

Have you tried the method in the link?

Can you post the modem name and IMEI? It is shown in the web panel.

Modem name: EC25AFFAR07A08M4G
IMEI: 358511020058461

Yes, I tried this but had no luck with it either.

I would like to add two things as a point of focus:

  1. I’m running the 15GB Tablet Unlimited plan, which essentially is 15GB of tablet hotspot data with infinite data use by the tablet, however the actual device ends up using the unlimited data as the modem itself is the “tablet”.
  2. After checking with ATT, the device’s IMEI was flipped to a Samsung IMEI automatically once this SIM was installed.

Some other things to mention: I tried this same SIM card (even after it was attemptedly fixed by ATT) on an RUT240 router with the same result, essentially being stuck in registered 3G with no connection allowed. I constantly monitored the SIM status immediately upon installation of the card, and here’s how things went:

  1. The SIM would initialize in 4G LTE with good signal strength, unregistered and no connection yet. This would last for about 3 seconds.
  2. The SIM would immediately flip to 3G signal, and be denied even the Operator. Lasts about 10 seconds or so.
  3. The SIM would register in the 3G network but remain in a NOCONN state (Disconnected), and stay here indefinitely.

Here’s some more info regarding diagnostics with RUT240’s

An RUT240 and SIM card with the same data plan. The SIM and RUT240 in this picture are not the problematic ones and are currently working properly as I write this message

Current RUT240 with the problematic SIM card (same card used in X750V2)

(Forum did not let me embed two images)

@alzhao Would you be able to elaborate further on how the device is registered as an IoT device with ATT, and what that means for picking a data plan?

Maybe just go to ATT and change one SIM card.