I have created a dynamic material Instance that I use for a health bar. It works as expected on the windows platform. When deployed to Android it does not show. I have exported from both 4.02 and 4.1 versions of UE4. The android device I am currently using is the samsung galaxy S4.
edit: To test I opened the blueprint_HUD example and then clicked on the mobile preview option in the editor. Everything is drawn on the screen correctly except for the health bar. I have hit a wall with this problem and hope someone else has found a solution.
edit2: While I have not resolved the issue of drawing a material to the hud, I have replaced the draw material nodes with draw texture nodes and that seems to be working on the android device.