Sorry, I forgot to mention that if you are on the Mac, the Log is under the Window menu. I'm glad you found it.
Although those log messages don't mention hover labels explicitly, they are telling us that there are features or combinations of conditions in the graph that are not supported in Interactive HTML This prevents all interactions with the graph including the display of hover labels.
The two messages indicating this are:
-Graphs with nested Y and Order By are not interactive.
-Heatmaps with size roles are not interactive.
Interactive HTML cannot support all the combinations of features of JMP. Both of these are such limitations.
For the first, instead of the two variables on the Y Axis, you could try applying the left most variable to a Y Group role. This will avoid the nested Y part of that limitation.
The second message is due to a variable applied to the Size role with the heatmap element. To avoid this limitation, you would either need to choose another element type or remove the variable from the Size role. Unfortunately, neither of these will result in a graph that looks like the one in your image. For example, if you choose to remove the size role, each heatmap cell will be the same size.
~John