Export is limited in the trial version, but there are a few map styles that you can export. These will be exported with a watermark, but are still useful for testing generated maps on your unit.
To export a map for a Lowrance unit from the trial version, you must use "Export Preset Style" and choose one of of the shaded relief or flat raster map formats. To see these maps properly on your unit, you must enable Shaded Relief (otherwise you will see the contour lines, but not the coloured background).
If you would like examples of pure vector maps for Lowrance I would be happy to send you one to test.
thanks,
Matt