MaxSea and NOAA ENC Charts
How are you trying to open the chart? I use "file -> open chart" and Maxsea then scans my system to find all available charts. I then go to "windows -> new chart window -> vector window" and , voila, there are the S57''s.
One problem with S57''s is that there is no world scale chart, so when the vector window is first opened, you won''t see the world and have no way to zoom in to the US to see the NOAA charts. Turn on the tides display, which will give you a rough outline of the coast, then zoom in using it as a sort of reference. I''ve enquired of Maxsea if there''s a way to open a specific chart, but their support is horrible and they have not answered the question.