In my iTunes library there are many tracks that have the cloud with embedded arrow (indicating that I need to download them from the cloud), but which are grayed-out, so that I can't download them, play them, or do anything. Can you tell me what is wrong?
You have probably already looked into this, but it sounds like "iCloud Status" is enabled in iTunes, but "iCloud Download" might not be. Go to
View > View Options
and make sure that "iCloud Download" is checked off.
Check that "iCloud Status" is being included in your current View->View Options, and see what it says for your greyed-out tracks. For me this shows all my grey songs as "Waiting", even though my iCloud Download icon shows the download arrow -- indicating that these songs never uploaded to the iCloud like they should have (for whatever reason), but that iCloud knew they were supposed to.
And troubleshoot from there...