- Make sure to turn off any lock screen passcode or Touch ID.
- Make sure to turn off Find My Iphone
- Make sure you restored or updated your device in iTunes and not OTA. OTA updates can cause problems
- Backup your device using iTunes.
How to jailbreak iOS 8.0 to 8.1.2 on Windows:
Step 1: Download TaiG jailbreak for Windows from here.
Step 2: Connect your device to your windows computer, and run TaiG.
Step 3: Uncheck the second option below Cydia to prevent installing TaiG app store.
Step 4: Click on the big green button to start Jailbreak.
Step 5: TaiG will now jailbreak your device. Do not disconnect your device during the jailbreak process. Once the jailbreak process is complete, your device will reboot and you will have Cydia installed on the home screen.