Some newer Huawei firmwares require digitally signed update files. You cannot bypass this without a Huawei enterprise account. Your only option is to get signed firmware from your ISP.
Common hardware versions for HG8245h:
Recap of success steps:
Used when web interface is corrupt or for batch upgrades. Huawei Hg8245h Firmware Upgrade
Never attempt a firmware upgrade over Wi-Fi, as a connection drop can brick your device. Backup Settings: Some newer Huawei firmwares require digitally signed update