This is for advanced users. Mistakes can hard-brick the device.
That means the router’s signature check rejected the file. Either the download is corrupted, or it’s not intended for your exact hardware variant. Redownload from an official source. b312-926 firmware
Never download firmware from random file-sharing sites. Unofficial firmware files can contain malware, brick your device, or permanently lock it to an unusable state. This is for advanced users
Go to consumer.huawei.com → Support → Downloads. Enter “B312-926” and search. You may need to provide your product’s serial number. brick your device