# Devices

Device configurations or software can sometimes cause connectivity to fail. This includes the application software and the GSM module/ chipset and its firmware as well. 

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If this SIM and device combination has worked before but not anymore, make sure you have not changed any configurations. Update the firmware to a previous version.
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If it is a new device you are using for the first time with the SIM/eSIM and you are experiencing issues, check the below items:

<details>

<summary>Are you registered to the network?</summary>

Try the SIM in a different device, preferably a different model as well. If it works, then it’s likely you are facing a device specific issue. Using a mobile handset can be convenient & quick to verify plug-in SIMs’ functioning. For eSIMs, use a different IoT device, if available.

</details>

<details>

<summary>Are the data settings entered correctly?</summary>

The basic settings for data connectivity are:

* Cellular Data is ON
* Data Roaming is ON
* APN is configured correctly

</details>

<details>

<summary>Is the APN entered correctly? Does the APN match the active connectivity profile on the SIM?</summary>

The APN should be based on your active connectivity profile. It is possible that the SIM has a different active profile from the APN entered in the device.

</details>

<details>

<summary>Try restarting the device</summary>

It is possible the configurations need a restart to take effect. If you are having to reboot the device often, it indicates a deeper problem that could be related to your application/ module firmware getting stuck.

</details>

<details>

<summary>If eUICC functions are not working properly</summary>

A device needs to be compliant to the following SIM ToolKit (STK) commands as a minimum for eUICC functions to work. Click here for full details:

* Bearer Independent Protocol&#x20;
* Refresh
* MO & MT OTA (binary) SMS processing
* Timer management
* Polling

</details>