A bricked watch does no longer boot. It typically stops at the boot logo and waits forever. This can happen for example, if a flash of the system image failed and the boot image can no longer boot the system. In such cases, you cannot reach adb from the command line, so there seems to be no way to recover the watch. Fortunately, it has been discovered how fastboot can be entered without a running system.
Source: TUTORIAL: Unbrick your Huami AmazFit Smartwatch / Xiaomi AmazFit PACE
