lenovo tab 3 7 plus tbalet fell down and wont turn on.

If you dropped it, something may have gotten jarred loose, or it may well be damaged. Depending on the phone, and how easily you can open it up, you can just try to remove the battery, for about 5 minutes or so, and then put it back in and seeing if you can charge it. Without turning it on first. Wait until it is charged fully (if it shows that it is) before you try.

If the device is still under warranty, and it is not a simple battery removal, try to contact the manufacturer about a repair or replacement so you don't void the warranty.