Connected to iTunes store, but can't download previously purchased items?

Question

When I set up a new computer last week, the Home Sharing process left a lot of holes in the iTunes library on my new computer.  I went to the iTunes Store to download previous purchases in an effort to to fill some of the gaps.  Initially, I was successful -- though the iTunes store would only download a couple of hundred files at a time.  However, I can  no longer make the "download previous purchases" function work, even though I still have around 350 files that it recognizes as available for download.  When I click the "download all" option and enter my password, I consistently get a message like, "This item is currently unavailable.  Try again later."  This has been going on for more than a week.  What can I do to make this work? 
As a separate matter, iTunes only seems to recognize about 1100 of my previous purchases, though the real number is probably closer to 3500-4000.  That is not critical, since I had MP3 backups for almost all of my ITunes purchases on an external hard drive.  However, the process of reconstructing my library probably would have been easier if I could have restored more directly from iTunes.  If anyone has encountered this kind of problem and figured out how to solve it, I'd be interested in case I ever have to go through the process again. 

Answer 1

I had an issues similar to this with purchased music not all that long ago, and rebooting (I think) is what got it working for me again.
See if this helps - sign out, restart, sign in again and try again.
Settings>iTunes & App Store>Apple ID. Tap your ID and sign out. 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.
Go back to Settings>iTunes & App Store>Sign in and then try again.
I would suggest rebooting the router - unplug it for about 30 seconds, and you can try that - but I'm not sure if that will help. It won't hurt anyway.