Huawei does not publicly provide ONT firmware downloads on their support website. Their official page notes: "Huawei ONT is used with an OLT and NMS of a required version. If the versions are not the required ones, the ONT may not work. If required, contact your internet service provider to obtain the correct ONT firmware or software."
Request a firmware push or ask them to email you the matching .bin or .tar firmware file. huawei hg8145v5-v2 firmware download