I forgot password, and the Samsung tab S was left in corner more than a month. I followed all instructions nothing worked. Here’s how you factory hard reset your Galaxy Tab 3 10.1 (GT-P5210): 1. Power off the device, do not charge it. Tablet should be completely off. 2. Wait for 20 Seconds. 3. Press and hold the Volume Up + Home + Power buttons for 15 seconds and release them. You get to the recovery screen. 4. Using the Volume Up/Down buttons navigate to Wipe data/factory reset Press the Power button to accept the option – this will take you to the confirmation screen. Using the volume buttons navigate to yes and press the power button again to confirm the action Your device will reboot. Mission accomplished!