I have a 1870F which I purchased in Nov 2016, it only uses the C-Map4D. I have the St.Lucie to New Orleans Card and according to C-Map, I'm supposed to be able to see the contour lines, VAD is unlocked. However, there's none visible. Can someone advised, step by step, on the settings so I could be view them. I have everything turned on, including High resolution bathymetric but I only see the normal chart info. Am I missing something to do? Little frustrating w/this unit. Thanks.