Very weird but I suspect it could be settings related. My examples are for an Axiom+ with Lighthouse 4. Note, you should be looking at an area covered by your chart, as any other area will be very basic (but should still show depths).
On the Chart screen
settings select Cartography. Make sure that Nautical Chart is selected - this will be the chart on the SD cart. For whatever reason the Lighthouse Charts
option is selected by default and that won’t show any detail if you haven’t bought Lighthouse. Note that each chart view has its own settings.
Next, check the Layers menu. Select Medium or High to see depths.
Next, check Depths and that you’re viewing all depths.
Check Advanced and that all the elements you want are selected for display.
On the chart screen
select the mode you want. Simple, Detailed, Fishing
, and Racing
modes all show depths. We use either Detailed (basically shows everything available in the chart) or Racing
(removes data not related to depths).