I'm not sure I have your answer but I'd like to offer a couple of points...

1. It's impossible for POI's to not be in the GPS if you saw them in mapsource, created a gmapsupp.img map using mapsource and copied the gmapsupp.img to the proper folder on the GPS or SD. The POI's are part of the gmapsupp.img and will be there for all the map segments you selected when creating your mapset.. There must be something else wrong that you are missing.

2. There are no VIA's to see, there are only POI's (points of interest). VIA's are points YOU manually add as part of your route. A via could be any POI, any Favorit, or any point on the map.

3. If you have both North and South American maps both installed in your GPS searches will not work properly (if at all) if both maps are selected for use at the same time. This is because they have overlapping geographical areas (Florida for one, and if I remember correctly, some of the Carribbean Islands.

You say your POI list is empty....
That is usually an indication that
a) you map did not load correctly
b) you have not selected the map for use
c) you have 2 or more overlapping maps sellected