Why is the SIM card of IRT08 not working or not recognized?

Please check what is displayed on the network side of the lower right corner after inserting the SIM card:

1. No operator name and no network signal strength in the lower right corner of the device: the sim card is inserted backwards, please restart the device after installing the sim card correctly according to the manual.

2. There is operator name and no network signal strength in the bottom right corner of the device: the local mobile network band of this operator is not supported.

3. There is operator name and network signal strength in the lower right corner of the device: IoT card (traffic card), the request for network access has been rejected by the operator's core network backend, please call the operator to cancel the restriction.