If you have a later MS install i don't think it will work properly, if at all, with BCs. Probably Garmin nobbled MS intentionally after they released HP for use specifically with BCs. You could try an earlier MS version from the old Perry Index on the Wayback Machine:
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There's been occasional references to Navionics but nothing recent or of any importance as far as i can see, like these: [Only registered and activated users can see links. ] and [Only registered and activated users can see links. ].

That's an old dirty trick by software vendors, start charging an annual renewal fee or raise the price once their stuff gets popular enough to get away with it.