Error "Only the latest version of a file can use Quicken Cloud"

This is actually one of the better error message in Quicken, in that it contains a somewhat decent explanation.

Every Quicken file is associated with a Quicken Cloud account. Even if you don't download transactions or use the mobile app, there's still a Quicken Cloud account associated with your file. If you do use one or more of those online services, they all utilize that Quicken Cloud account. If you go to Preferences > Connected Services, you can see the name of the associated Quicken Cloud account (which is normally the same as your Quicken file name). You can also click on See All Cloud accounts to see all the Quicken Cloud accounts you've generated (which is sometimes a surprising number if you've duplicated, copied, restored files over time). 

The first thing to make sure of is that the Quicken file you have open currently is your actual current data file. Sometimes w make duplicates, or open a backup copy, and accidentally end up in an older version of our data than the most current. If you're sure that you are indeed using the most recent copy of your live data file, you can simply click the Reset button in the Preferences window. Reset will wipe out the existing Quicken cloud account associated with this file and create a new one based. If this is your current file, that's exactly what you'd want, so resetting Quicken Cloud should be no problem.