The “symptom” you describe sounds very much like in this topic:
If you connect your FP3 in fastboot mode to your computer and launch command prompt on your computer, you could try if “fastboot oem unlock” works.
The “symptom” you describe sounds very much like in this topic:
If you connect your FP3 in fastboot mode to your computer and launch command prompt on your computer, you could try if “fastboot oem unlock” works.