Possibly incorrectly installed? Go through and double check everything, and make sure you follow the guide step by step, taking NO shortcuts. iFixIt doesn't have a guide for this one, sadly; just use the one you've found.
Hello, If you are unable to factory reset your device through the settings menu (Settings>Backup and Restore>Factory Reset) You can try to format it by booting into recovery. In order to do so, Power off the device. Press and hold the Home button, power button, and the volume up button simultaneously. From there, use the on screen instructions to reset the device. Cheers and best of luck!