You've exceeded the maximum number of datasets?

The two things I can tell you is that we have been told that restoring from a backup does create a new dataset and as such shouldn't be a "regular practice".

The second thing is that I test a lot of things that have me needing to revert back to an old copy.  The way I do that is open an old copy.  I don't use Quicken's restore.  Note you can just rename a .QDF-backup file to .QDF and it will open without going through Quicken's install.  At any rate, in all the years that I have been doing this I yet to have this error pop up for my main data file.  So, I suspect this is "clearer" way to go.

But also note that I don't use some of the features that rely heavily on the Quicken Cloud dataset.
I don't use these features:

1. Sync to Mobile/Web  (Syncs transactions, budget, categories, ... to dataset)
2. Quicken Bill Manager (Syncs data for the bills to the dataset)
3. Express Web Connect (Syncs transactions to the dataset)

Note I know other users that are using Express Web Connect and not having the problem, but they might also not be in the situation where they resort to an old copy very often.