No signal/network issue
1. Please check if Airplane mode is switched off.
2. If you are using a ZTE device, please make sure the SIM card is enabled from Settings > SIM & network > SIM 1/ SIM 2.
3. Make sure the location/area has good network signal, try different locations if possible. Please note that if there is any signal interface or shielding then it might cause low or no signal issue.
4. Make sure the SIM card works by trying it on another device.
5. Eject the SIM tray and insert again to make sure SIM is inserted properly.
6. There may be situations wherein your network provider might deactivate your SIM card, so please do check with your network provider.
7. Make sure the SIM card is not purchased with other contract devices.
(If the ZTE device was purchased in contract with O2, then other SIM cards will not work with the phone)
8. Select the right network type from Settings > SIM & Network > Preferred network type.
9. In Roaming status, network availability can also depend on prepaid plans, monthly billed plan and the region. Please check this with your network provider.
10. Please make sure the device has the latest firmware installed.
You can check this from Settings > System Updates.
If the issue is not resolved after performing the troubleshooting steps, please contact our customer support team for further help.