If you are seeing the error on your OnePlus device, it means you are trying to write new firmware or system partitions while the bootloader is still security-locked. This is a safety feature designed to prevent unauthorized software from being installed on your phone. Why This Happens
T-Mobile branded OnePlus devices (e.g., OnePlus 8T+ 5G) have permanently locked bootloaders. Even with OEM Unlocking enabled, the fastboot oem unlock command returns a permission error. flashing is not allowed in lock state oneplus
The error occurs when:
fastboot devices fastboot flashing unlock If you are seeing the error on your