Smileys disappeared from iPad Pro

After updating my iPad Pro to iOS 10, I downloaded the animated Smileys from the App Store. It worked for awhile, but now the Smileys have disappeared. The App Store shows the Smileys as being installed, but they no longer show up in iMessages. How do I download them again or otherwise fix this problem? (I have already tried restarting my iPad, but it didn't help.)