I just purchased Outline for Mac, installed it & license. I have owned Outline for iPad for years. I thought the sync would be automatic, and it was not. After researching on net I found a tab inside Outline for Mac for iCloud sync and in parenthesis is the following "iCloud Drive (available only for the Mac App Store version)". Okay. So I then went to the App Store to see if it is on the App Store- and it is not.
WHAT'S GOING ON?!
I will only use iCloud Drive and not DropBox or any other service.