It never fully locks into 4G. It just gives the generic “SIM card is not registered” error which seems to be a default error message. The UI does not display 3G/4G or show signal bars.
I’m starting to think AT&T has just banned your devices from their data plans at 4G speeds.
I tried locking it to band 12 and got similar results, including “state LIMSRV”.
Now here is something weird. I tried putting my cell phone sim card into the x750 and it made a 4G connection. So this is definitely a compatiblity issue between AT&T and the x750.
I wouldn’t band lock until you find what band(s) your local AT&T tower uses, does the phone tell you? According to the AT&T site they use these bands for LTE
My phone is an unlocked at&t phone whch connects on band 12. My current cell phone plan is an AT&T MVNO but my previous plan was with AT&T directly. I’m fairly certain I am not out of AT&T’s LTE coverage area.
So to summarize, you know of this problem and are unwilling or unable to fix it. But you still advertize this router as “AT&T certified” which is now a completely meaningless and borderline fraudlent claim.
Thank you for wasting my money and time. I don’t know why I expected anything different these days.
For anyone finding this via google, The plan I am trying to use is AT&T’s 100GB/$55usd prepaid data plan bought directly from AT&T. A fully legitimate plan meant for devices like the x750. And this is not some obscure plan; it is one of the primary plans offered for AT&T prepaid service.
I can also confirm that I am experiencing the same problem with my X750 on Cricket, which uses the AT&T network. I have 5 lines on a family plan with one of the SIM’s being in this router. All phones in the house connect to LTE just fine, but the router never does (only 3G/4G, which limits speed to 3MB/s). When taking the SIM card out of the router and putting it in a phone, it connects to LTE with no issues. There appears to be some compatibility issues with the X750 and the ATT network currently.
For those coming here from a google search: I’ve done some more research and found this:
The x750 may be caught up in AT&T’s phase out of all 3G service. If so, than this situation is permanent. The x750 will no longer be able to connec to ATT at 4G, and in Feb 2022 it won’t be able to make any connection at all.
SIM card cannot be registered. Please check: 1. You are using the compatible modem for your carrier; 2. Whether a specific APN or data plan is required.
For a few seconds it would connect as shown here but then 3g/4g symbol is gone and it gives the above error message. I then have to reset the modem because I cannot connect to the internet.