Android-based devices (including Huawei’s set-top boxes) have a dedicated partition called recovery . This contains a minimal operating system used to apply updates, wipe cache, or perform factory resets. Unlike a standard boot, loading this partition is usually triggered by a specific key combination or a command from the primary OS.
This failure usually occurs when the system detects that the recovery or boot image has been altered or corrupted. Common triggers include: huawei s7721u recovery image verify failed link
Are you trying to install a or an official stock update ? How to Fix Huawei Recovery Image Verify Failed Error huawei s7721u recovery image verify failed link