Hi there. In order to give you more precise info we need to know if you're running stock or custom ROM? Otherwise, the general procedure would be to reinstall the Samsung Home application. If that fails, I would recommend wiping (data/factory reset) as it would probably reinstall the app along with any corrupt system files.
How to wipe Galaxy Tab:
1) With the device off, press and hold Volume Up and Power.
2) Release the Power button when you see the Samsung logo, but continue to hold Volume Up until the recovery screen appears.
3) Use the Volume buttons to navigate the menu and select wipe data / factory reset. Press Home to choose the selection.
4) Press Volume Up continue.
5) The Galaxy Tab should then go through the hard reset process.
Let us know if that helps. Good luck.