Why can't I download any apps

That is a a very broad question without more details.

Do you have restrictions enabled? Settings>General>Restrictions>On. If so, you may have disabled the ability to download apps,

Are you signed into your Apple ID and iTunes account on the iPad? Settings>Store>Sign in?

Are you trying to download apps larger than 20 MB via 3G which is not possible to do?

To answer your questions, not that broad

..restrictions are not on

..yes, logged in to account for iPad in App store

..No, all small apps.

Without details - yes it it. However, you provided some details. Does anything happen at all when you try to download? Do you get a "waiting" or a "loading" icon on the screen? Can you download in iTunes?

Have you tried the basic troubleshooting steps?

Restart the iPad by holding down on the sleep button until the red slider appears and then slide to shut off. To power up hold the sleep button until the Apple logo appears and let go of the button.

Reset the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider - let go of the buttons.

Quit the app store app and restart. In order to quit or close apps - Go to the home screen first by tapping the home button. Quit/close open apps by double tapping the home button and the task bar will appear with all of you recent/open apps displayed at the bottom. Tap and hold down on any app icon until it begins to wiggle. Tap the minus ➖ sign in the upper left corner to close the apps. Restart the iPad. Restart the iPad by holding down on the sleep button until the red slider appears and then slide to shut off. To power up hold the sleep button until the Apple logo appears and let go of the button.

i got this massage There was an error in the App Store. Please try again later. (100)

also i use macbookPro