Connectivity issues: why a SIM won't connect

A Simbase SIM that won't connect is one of two problems: it isn't registering on a network at all, or it registers but no data passes. The causes differ, so work out which one you have first, then run the checks below. Most take under a minute.

Start with Diagnostics

Open the SIM in the dashboard and run Diagnostics before anything else. It checks provisioning, network status and hardware band compatibility automatically, and usually points straight at the cause. See Diagnostics.

If Diagnostics comes back clean, work through the checks below.

Which problem do you have?

Open the SIM in the dashboard and check whether it is currently in session. Then look at its last registration attempts (under Diagnostics → Events) and network CDRs (under Data usage).

Session state is the quickest of the three to read, so check it first. A SIM in session is online and able to pass data, which rules out most of the checks below straight away.

What you see	What it means	Checks to run
Not in session, no recent registration	The device isn't reaching a network	1, 2, 3, 6, 7
Recent registration attempts, but no CDRs	The device attempts to register but isn't attaching	3, 5, 7
In session, but no CDRs	Session open, nothing being sent	4, 7

What you see

Not in session, no recent registration
Recent registration attempts, but no CDRs
In session, but no CDRs

Account-side checks

1. Is the SIM enabled?

A disabled SIM cannot attach to any network. Open the SIM and confirm State is Enabled. See SIM state.

If it is disabled and you did not disable it, something switched it off. Usage limits, Auto-Disable, Theft protection and a zero balance can all do this. See SIM disabled unexpectedly.

2. Is your account balance positive?

A zero balance disables every SIM on the account, not just the one you are looking at. Check Billing → Overview. Once you top up, service resumes within minutes. See Account balance and invoices.

3. Does the coverage plan include the country?

A SIM can only attach to networks included in its coverage plan. A device that worked in testing and fails after shipping abroad is usually this. Check the plan against the deployment country and switch to a wider plan if needed. See Coverage.

A device attempting to register on a network outside its coverage plan will usually show rejected location updates. You can see these under Diagnostics → Events, and they are a strong signal that the plan, rather than the device, is the problem.

Device-side checks

4. Is data roaming enabled on the device?

This is the single most common device-side cause. A Simbase SIM is not registered to a local operator, so it roams onto every network it uses, including in the device's home country. If data roaming is off, the device still registers on the network, and SMS still works, but no data session opens. The SIM looks connected while nothing passes.

Enable data roaming in the device or modem settings. On routers it is often labeled "Permit roaming" or "Data roaming". See Data roaming.

5. Is the APN correct for your SIM profile?

The second most common cause, and the one people most often get half-right. Two things go wrong:

The device auto-detected an APN. Android in particular guesses an APN from the SIM's MCC/MNC, and the guess is usually wrong. Delete any other APN profiles and set the Simbase APN explicitly
The APN is right for a different profile. The correct value depends on your SIM profile and whether a fixed IP is assigned

SIM profile	ICCID range	Standard APN	Fixed IP APN	Alternative APNs
Black, Red, Green	89103*	`simbase`	`fixedip.us` or `fixedip.eu`	`simbase.us` or `simbase.eu`
Blue, Yellow, Cyan	89445*	`simbase`	`fixedip.m2m`	`mobiledata`

SIM profile

Black, Red, Green
Blue, Yellow, Cyan

On 89103* range profiles, simbase.us and simbase.eu force a specific breakout location instead of letting simbase choose automatically. On 89445* range profiles, mobiledata is a fallback to try if simbase doesn't attach.

No username, password or dial-up number is needed. If the device asks for them, leave them blank.

APN changes only apply to a new data sessionAfter changing the APN, reboot the device or use Reset connection in the dashboard. Until the current session ends, the device carries on using the old value and nothing appears to change.

6. Do the device's bands match the local carriers?

If the account and APN are correct, the hardware may not support the frequency bands or network technologies used where it is deployed. A device built for North America often lacks the right bands for Europe, and a 2G-only device will never connect in the US, Canada or Australia, where 2G has been switched off.

Diagnostics checks band compatibility. See Compatibility check.

7. Is there an ongoing incident?

If several SIMs stopped working at once, or a SIM that has been running for months goes quiet with no change at your end, check the Simbase status page at simbasestatus.com before investigating further.

Incidents affecting a single operator or region are not always visible from one SIM's Diagnostics result. The status page is also where maintenance windows are announced, so it is worth checking whenever the timing of a failure looks suspicious.

Never leave a disabled SIM in a powered deviceA disabled SIM keeps retrying registration and is rejected every time. Depending on the reject cause and how the modem is configured, those rejections can add networks to the FPLMN list, the list of forbidden networks stored on the SIM. The modem reads that list during network selection and skips anything on it, so it stops attempting those networks altogether. This is a common reason a device still will not attach once you re-enable the SIM, and the list survives a power cycle. A ban by the roaming partner is possible too. Power the device down or remove the SIM before disabling it.

Still not connecting

Contact support with:

The SIM's ICCID
The Diagnostics result
The deployment country
The device make and model, and the APN you set
Screenshots of the APN configuration or device-side logs are welcome

Common questions

A Simbase SIM is not tied to a local operator, so every network it uses is a roaming partner. With data roaming disabled the SIM still registers and SMS still works, but the device won't open a data session, so there's no internet.

It asks the network to drop the device's current session so it reattaches. It is the fastest way to apply an APN change without physical access, though the request does not always succeed, depending on the hardware and the current carrier.

Not from the SIM. Simbase SIMs are non-steered, so the device chooses the network. Most IoT routers let you set a preferred network list in their own settings. See Optimizing device configuration.

That means it registered on a network but the data session isn't opening. Check data roaming and the APN, checks 4 and 5 above.

Diagnostics, automated checks for a single SIM
Set up the APN, the APN for your profile and use case
Data roaming, why roaming applies everywhere on a Simbase SIM
Coverage, check the plan covers your deployment country
Compatibility check, confirm bands and technologies before deploying

Quick answer

Why is my Simbase SIM not connecting?Check four things in order. The SIM must be Enabled, the Simbase account balance must be positive, the coverage plan must include the country the device is in, and data roaming must be switched on in the device settings. If all four are correct, the APN is the usual cause. Run Diagnostics on the SIM first, since it names most of these directly.

Updated 5 days ago

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