SIM7600 in OVMS board - T-Mobile - Registration Denied

I’ve got a Hologram SIM in an OVMS (Open Vehicle Monitoring System) board with a SIM7600 modem. It had been working reliably well over the past month or so since I bought/installed it. Yesterday, I went to check on it (as I do at least daily), and it had been offline for the past 4 hours.

I headed over to the Hologram website, and found a recent incident reported that sounded about right - so I ignored it and carried on, knowing it’d be fixed soon.

Today, I check again - it’s still offline, and the incident doesn’t make any mention that devices may still be offline, so my eyes go to local device issues. I dig deeper – Hologram portal shows it’s “connected”, but 0-byte recent sessions, as such:

Not great. I check in locally, and I’m slapped with “DeniedRegistration”:
(evidently I’m too new a user to post 2 screenshots - but imagine this, but in an image:)

MODEM Status
Model: SIM7600
Network Registration: DeniedRegistration
Provider: T-Mobile Hologram
Signal: -53 dBm
Mode:
State: NetWait
Mux: Status up
PPP: Not running
GPS: Connected on channel: #1

Well, heck. I’ve tried the one thing I have available: “resume data”. No improvement. Stopped/started the modem (power cycle), no change.

Anyone else, perhaps still affected?

I’m still dealing with this - and after digging deep into the modem and with OVMS support, it’s increasingly likely a Hologram issue, somewhere deep in network guts. I’ve now got the modem configured for LTE-only, and it has no FPLMN (all F’s). It flops randomly between DeniedRegistration and RegisteredRoaming states.

Ting SIM, however, registers just fine (but can’t seem to get through to PPP).

The few occasions it (with Hologram SIM) does get registered, though, traffic gets through fine.

There may be some hardware issue (I suspect the SIM7600 isn’t the most… robust… cellular radio design in the world), but there’s absolutely no hint of that in the Hologram portal (which continuously says everything is fine and the device is online). The modem itself is reporting a registered state of “1,3” - 3 meaning “denied”.

The saga continues unabated.

Hi can you confirm the modem is using the correct “hologram” APN? You may want to email our support team about this

Yep, all the low hanging fruit has generally been picked. APN is “hologram” as it should.

How do I set the APN? – Hologram

I have a SIM7600G-H that I use pretty reliably when I need to test out an LTE modem here. I am assuming you have some ability to send AT Commands. Reaching out to support they can check the signalling logs which might help suss out whatever problem you are running into but they will likely ask for a modem diagnostic so you can get ahead of that by following this guide: https://support.hologram.io/hc/en-us/articles/360035697393-Modem-SIM-Annotated-Diagnostic-Test

Unfortunately that day we did have several issues so its hard to know if your original issue is related to the delayed usage reporting or the signalling issue. I will say the signalling issue was a very small subset of SIMs so its more likely that screenshot posted was due to the usage reporting being very delayed but support should be able to at least see what the tower is reporting and why it might be getting denied.

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Actually, it gets a bit deeper than that.

(Overall registration status?) AT+CREG? 1,3 (translation: Denied)
(LTE/E-UTRAN registration status?) AT+CEREG? 1,5 (translation: Registered, Roaming)

The modem firmware seems to be mixing its wires up. Even with all modes except LTE disabled, the modem returns “registration denied” (state 3) for its “CREG” command, but returns “registered roaming” for its “CEREG” command. So it’s confusing the heck out of the firmware.

At least I think we’re getting to the bottom of it.

Conclusion appears to be: T-Mo started denying my SIM access to voice and SMS functions (as expected – this is good), but did so about a month after starting service. That started confusing the OVMS firmware, because it queries “CREG?” to operate its state machine – and CREG is basically for voice network registration, while C*REG (CEREG, CGREG) is for packet switched data – which is all we care about!

If I send the manual command “AT+CEREG?” using the OVMS console command “cellular cmd AT+CEREG?”, it instantly pops online (at least, with a new “CEREG?” response listener, part of “edge” snapshot firmware 3.3.002-47-gfd3554f7). Working with the devs to get it to more reliably query “AT+CEREG?” instead of “AT+CREG?” especially considering the modern world of 2G & 3G sunset - CEREG/CGREG are the only useful commands now anyway.

Of course, I’m interested in being corrected if CREG is supposed to be a more broad “registration status” command – but as of now, it’s always returning “1,3” - registration denied.

This provides some interesting context on C*REG commands: mobile - CREG, CGREG, CEREG AT commands - Stack Overflow

I commented on that stack overflow question. It’s very helpful. In my code I now check if any of CREG, CEREG, or CGREG respond with 5. I may be completely screwed because I have several customers with units with old firmware that look only for CREG. With you understanding of this issue, do you think that is the case?

Sorry I didn’t see this thread earlier I may have thought to point you that SO question.

@FalconFour FalconFour You don’t happen to be in Canada do you? I’m in Texas and am still getting 5 for all three REG statuses, but I’m concerned my Canadian customers might only being seeing CEREG == 5 and CREG = 3. Maybe that’s why my Canadian customers’ units stopped working with the new Hologram Hyper SIMs that Hologram really wants us to use (their units are working fine with the old SIMs).

Nope, US/San Jose here. :confused: But hopefully this is a good clue!

Maybe there’s still something Hologram could do… would have to dig into why CREG returns “denied” but CEREG returns “all good!”. I would seriously think CREG would be the overall/master registration command, and C*REG would be the “how registered are you” commands…

I would also have hoped so, but a few months ago I got this with one of my “new profile” Hyper SIMs on AT&T. All three REG statues were returning 5 when I forced it to T-Mobile using AT+COPS=…

But on my regular Non-Hyper SIMs I think REG is working fine.

Unfortunately my modem is not smart enough to try the next network on the list of AT+COPS=?

15:58:16.898 -> at+creg?
15:58:16.898 -> +CREG: 0,3 
// NOT registered circuit-switched on AT&T
15:58:16.898 ->
15:58:16.898 -> OK
15:58:19.355 -> at+cereg?
15:58:19.355 -> +CEREG: 0,5 
// YES registered LTE on AT&T
15:58:19.355 ->
15:58:19.355 -> OK
15:58:23.333 -> at+cgreg?
15:58:23.333 -> +CGREG: 0,5 
// YES registered GPRS on AT&T
15:58:23.333 ->
15:58:23.333 -> OK
15:59:02.784 -> at+cops?
15:59:02.784 -> +COPS: 1,0,"AT&T Hologram",7 
// we're on AT&T