The Huawei B311221 exists in at least four hardware revisions. You cannot use a firmware file from a different variant.

Huawei uses a strict versioning system. Installing the wrong firmware can:

Huawei no longer distributes consumer firmware directly. Instead, your ISP provides it.

Are you experiencing a specific or error code that requires a manual firmware flash? How do I update the firmware version of my HUAWEI router

Never disconnect the power supply during a firmware update, as this can permanently "brick" (damage) your router. HUAWEI Global once you have the firmware file?