Settings > Edit Intensity Zones > the last column. Make sure there are values in there. I just have 0,1,2,3,4,5, but I'm not really sure what they do so there are probably better ones. Then I think it'll show up on your log as long as it's a past date range (not just the current "your log" view), so hit the little arrow to go back in time a week, then forward.
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