My solution for iTunes Home Sharing not working:

Until Apple fixes the problem:

This has been working EVERY TIME:

Connect your iPad/iPhone to your iMac via Bluetooth when iMac is awake.

Now when iMac is sleeping and

When iTunes shared library doesn't show up, turn on Bluetooth on your iPad/iPhone and click on your iMac connection.

Now I have found whether or not the device connects to the Mac, the connection to the shared library can now be made through the other apps.

Try it, it has worked EVEY TIME.