Step 1: Long press the power button of the iPad to turn it off.
Step 2: Connect the iPad and the computer with iTunes installed with a data cable, and open iTunes. Note: The account logged in by iTunes must be consistent with your iPad account.
Step 3: Long press the iPad power key until the white Apple logo appears on the screen, and then press and hold the home key until the black screen
(or press and hold the power key and home key at the same time until the screen goes black)
Step 4: After the screen goes black, release the power key, and still press and hold the home key until the iTunes terminal responds. Try a few more times. I tried twice and succeeded.
Step 5: Click "Restore iPad" on iTunes, and restore the iPad according to the prompt
Step 6: After the iPad is restored, it can be restored through the backup of iCloud or iTunes (refer to the picture and follow the prompts step by step). If there is no backup before, nothing will be left. Remember: iCloud backup should be opened to avoid data recovery after iPad restore.