This problem can occur if the Z-axis of the printer has been calibrated too close to the build-plate. Try calibrating the Z-axis manually by visiting “Printer tools” in the Sculpto App.
With bigger print objects, you can bend the flexible build-plate and thereby getting the object to release from the build-plate. You could also try to loosen the object from the build-plate using a dough scraper, spatula or something similar. Watch the video below to see an example of how it could be done.