It is recommended that you refer to the following methods:
1. Enter the settings, search for settings "data network", and check whether the "data network" switch is turned on;
2. Enter the settings and search for setting items "VPN". If VPN is enabled, it is recommended to try it after closing;
3. Make sure that the phone card is sufficient. If the arrears are stopped, please restart the equipment after the recharge is successful;
4. Please confirm whether the traffic restrictions have been met with the operator. After the telephone card reaches a certain traffic, it may be limited or restricted to the Internet;
5. If metal, magnetic suction cases or brackets are used, such external accessories have a shielding effect on the signal. It is recommended to try it out;
6. Enter the settings, search for setting item "access point" to be reset to the default settings, at this time, the default access point will be used. Can restart the device attempt
7. Open the flight mode and then turn off. Let the device re -search network register the network 
8. Contact the network operator to provide the latest network APN parameters;