When i click on the small box on ''Landing Autopilot'' it does not come up on the screen. I even Re-installed Mechjeb2 it did not seem to work again.

Open the debug log and see if there is any red error message ( ALT - F12, debug button) .
If you see some then open the settings panel and push "Restore factory default setting". This will delete your customisation but may fix things.

Ok, thanks i will try this after school and give feedback on what happens.

But where is the Restore factory setting?

here : http://imgur.com/stPVFaY