Gotta love the Cloud! Fooling around with a package, installing, uninstalling, removing, re-downloading and installing a different version, somehow got something tangled up somewhere so the package wouldn't work at all - nasty white page or nginx gateway errors. One click to restore the cloud to a point before I first installed, and now all is well. Package works beautifully, Revo is beautiful, and the Cloud is terrific.
Same thing counts for a broken installation after a vapor export/import.
Just re-install modx with the built-in update function of the cloud and you are up and running again!