Check to see if your desktop system shows as associated with your Apple ID. Instructions here:
If it's not, try downloading some previously purchased item from the iTunes Store. If that's successful, that should get your desktop system associated. Check the list in Managed Devices to make sure your system now appears. Then try the iTunes Match setup again.
Hope this helps.
I have found that the desk top is logged in as @me.com
And my laptop was logged in as @juno.com
I didn't know I had two acounts. I didn't mean to set them up like this. Is their any way I can get them put back togehter?