Have you tried this?
There are a few things you should try first when you experience problems with your device:
Detach the cover of the nano SIM card slot. Using the tip of a pen or similar object, press the OFF button. After the device is turned off, restart it.
Update your phone to ensure that you have optimal performance and the latest enhancements. Read more about how to update and find latest software version.
Reset your device to its original settings to remove memory blocks. Under Settings, tap Backup & reset > Factory data reset > Reset phone . Don't forget to back up any important data saved on your device!