If you are experiencing slow performance, you might try a (Settings > System > Reset options > Erase all data) before attempting a full firmware reinstall.

Confirm the selection. The device will reboot, install the firmware automatically, and boot back into MyOS.

Manually updates your device to the latest security patch or rolls it back to a previous version if a new update introduces bugs.

Click the (Start Downloading) button inside the flash tool. Power off your ZTE Blade V40 Smart completely.