Floorplan Editor is launched via the Assign Package Pins process (empty design mode); then, doing File->Import
and selecting a UCF file to import from does not work. The constraints will not be updated in Floorplan Editor View. What might cause the problem?
This is a known issue, and it is scheduled to be fixed in the next major release.
To work around the problem, launch the Floorplan Editor via the Create Area Constraints Process.