Around 2018, with the release of the and later chips (P20, Mate 10, P30 series), Huawei moved away from the legacy unlock code system. They introduced a server-side authentication model.
A SIM lock is a technical restriction built into a mobile device by network carriers. If you purchased a Huawei smartphone or modem through a carrier (like Vodafone, T-Mobile, or AT&T) at a subsidized price, the device is likely locked to that network. huawei unlock code calculator tool