If you just bought it today:
💡 Permission is often granted based on a daily quota that resets at 00:00 GMT+8 (Beijing time). If it says "Quota Reached," try again exactly at that time. Your Mi Account must be older than 30 days to be eligible. Phase 2: Binding the Account Unlocking Bootloaders - postmarketOS Wiki how to unlock bootloader in xiaomi poco x3 pro new
Xiaomi does not allow you to unlock a phone without digitally "binding" your Mi account to that specific device via the developer settings. If you just bought it today: 💡 Permission