Never use services that ask you to install strange software on your PC to "calculate" the code. These are often vectors for malware.
Historically, Huawei provided an official "Unlock Bootloader" page where users could request a code. , just before the P30 Pro was released. unlock bootloader huawei p30 pro full
Try a different USB port (USB 2.0 is more stable than 3.0) or a different cable. Never use services that ask you to install
You cannot simply plug the phone in; you need to put it into a specific diagnostic mode. run a command in ADB
Historically, Huawei allowed users to request an unlock code through an official website. Users would simply generate a code, run a command in ADB, and the phone would be unlocked.