I'm not sure if this is a bug or just a limitation of how Houdini Engine works in Maya but I can't get expressions to work on exposed parameters for my asset. For example, I have a “number of copies” control for a duplicate node but if I try to create an expression in Maya to drive it, the frame doesn't change:

building1.houdiniAssetParm_floors = time;

Any ideas?

Maybe this is because of the evaluation mode. In the Preferences -> Animation, and under “Evaluation Mode”, make sure “DG” is selected. The new evaluation mechanism is not supported yet.