If an OTA update fails, try restarting the phone or clearing the cache of the "System Update" app. What is the current status of your device? malfunctioning or bricked
Updates are often rolled out in phases. If you know one exists but can't see it, check again in a few days. Insufficient Storage: Ensure you have at least of free space for the update to download and unpack. Failed Installation: Firmware ZTE Blade A55
If you need to flash a full stock ROM: