I can't download apps iPad Air 2 some will some won't

If you haven't restarted the iPad yet, try that.

1. Press and hold the Sleep/Wake button until the red slider appears.
2. Drag the slider to turn your device completely off.
3. After the device turns off, press and hold the Sleep/Wake button again until you see the Apple logo.

Then try downloading apps.

If that doesn't help, check to see if your iPad has an iOS update available.

Tap Settings > General > Software Update

Current iOS is 9.3.3

See if you have Restrictions enabled > Use Restrictions on your iPhone, iPad, and iPod touch - Apple Support