To understand why V4 and V5 are difficult, it helps to look at the progression of Huawei's security:
The Huawei V4 and V5 unlock code calculators are third-party tools used to generate network unlock codes (NCK) for newer Huawei modems and pocket Wi-Fi routers. These specific algorithms (V4 and V5) were developed because older "universal" calculators cannot handle the security used on modern HiSilicon-based devices. download huawei v4 and v5 unlock code calculator link