A：Please check if your device can make calls. If it can, but all apps cannot use mobile data, please try the following steps:
1. Confirm that the data switch is turned on. Go to Settings or pull down the notification bar to check if the SIM card's data switch is turned on.
2. Check if the SIM card has data activation and if it is suspended due to unpaid bills.
3. If two SIM cards are inserted, you need to set which card to use for mobile data (a prompt to select the primary card will appear on the screen after inserting the card; if you don't select it here, you need to do so in Settings).
4. Go to System Settings > SIM Card Data Management to check if a data limit has been set.
5. Settings - System - Reset Options - Reset Network.
6. Inquire with your carrier whether the IMEI is locked. You need to contact your carrier to unlock it and understand the requirements for unlocking after re-entry into the network.
7. If the above factors have been ruled out and the problem persists, ask the user to capture log data and provide the IMEI and a video analysis of the fault.