Why did the bottom bar of IpAD suddenly disappear?

1, connect the iPad to the computer with a USB cable, and then you will see a page pop up on the computer, prompting that the connection is successful.

2. Turn off the iPad first, and then you will see a page pop up on the computer, indicating that the connection has been disconnected.

3. Now press and hold the power button for 3 seconds, and then continue to press and hold the On/Key and Home button at the same time until the first 10 second. Please immediately release the On/Off button and hold down the Home button until you see a USB device in DFU state on your computer, and then you will enter DFU mode.

4. At this time, iTunes will automatically start and prompt the recovery mode. You can press and hold the shift key on the keyboard, click "Restore" and select the corresponding firmware for recovery.