If the power indicator light stays solid red or blinks erratically, and you lose all connectivity after a failed update, you may need to perform a hard factory reset: Keep the router powered on.
Huawei likely chooses not to offer manual downloads to prevent users from accidentally installing the wrong firmware version for their specific hardware, which could permanently damage the device. The official stance is that if you need a firmware update, it will either happen automatically or be triggered by a manual check within the router's interface, as described in the official upgrade guide. huawei wifi ws5200 firmware download