Mac downloading from but not uploading to iCloud Drive
Since I upgraded to Yosemite and iCloud Drive a few weeks ago, my iMac (27", 2010) no longer uploads files to iCloud, but it does receive files and updates from other devices. For instance, if I add a PDF to the Preview app on my MacBook Pro (13" retina, 2012), it shows up on the iMac, but not the other way around - any file I add to iCloud Drive on the iMac winds up just sitting there with a little dotted cloud icon next to it in Preview, and does not show up on the MacBook Pro, my iOS 8 devices or icloud.com. I have files that have been stuck like that for over a week now. Has anyone else seen this problem? Are there any workarounds?
iMac, OS X Yosemite (10.10.1), 27", 2010