Save yourself the trouble .. I'm convinced it's an iTunes bug.
I talked to a Senior Tech, and created a brand new user on my system.
I signed in to iTunes store, and iCloud, and downloaded all my content again from iCloud.
The "Purchased" link worked again.
I though I had the problem licked until I noticed that some of my content had not been downloaded - in my case it was some iTunes LP and Digital booklets.
I downloaded one digital booklet, and it stopped working.
I switched to the 'songs' view and deleted the digital booklet and it started working again.
I tried a few different Digital Booklets in case it was a specific one - they all cause it on my system.
I have repeated the same on my Mac Mini, a MacBook Pro 2012, and an IBM Laptop (which was new and never had iTunes installed before.)
They all give the same result.
Bug in iTunes as far as I am concerned, I have a ticket open with senior Tech.
They had me reset the 'ACL' for the user, but booting up into recovery mode, it did not fix the issue.
I suggest you also open tickets too to raise awareness.