Buttons sometimes inactive in Simulation mode
I have not figured out under what conditions this happens, but in Simulation mode I sometimes encounter buttons that are not active when user hovers mouse over it (i.e. cursor does not change shape and it is impossible to click the button).
If you click somewhere within the Simulation area, then the buttons become active the next time you hover over them.
The last two times that I have encountered the issue was within a Dynamic Panel that hidden by default and then an event caused the panel with the button to display. Not sure if this is the cause, but ....