Please Flash - Unlock Token First Oneplus Better
On carrier-branded OnePlus phones, the bootloader is double-locked. Even if you have "OEM Unlocking" enabled in settings, the device will reject the fastboot oem unlock command until a valid token is flashed to the cust-unlock partition. How to Get and Flash the Token
If you want to follow the proper, official route to get your token, here is the step-by-step guide: please flash unlock token first oneplus better
Power off the device. Press and hold Volume Up + Volume Down simultaneously while plugging the phone into your PC via USB. The screen should display the Fastboot logo. Press and hold Volume Up + Volume Down
Which (Windows, macOS, or Linux) are you using on your computer? Visit the official OnePlus Unlock Token Service page
Visit the official OnePlus Unlock Token Service page. You will need to provide: Your IMEI number. The Unlock Code you just retrieved. A valid email address.
— Flash community-developed Android distributions like LineageOS, Pixel Experience, or Paranoid Android. These ROMs often provide longer update support, cleaner interfaces, and features not found in stock OxygenOS/ColorOS.