People had problems with 1.1 build that nothing happened after pressing hotkey. I didn't manage to have that problem, so i was quite confused at how to fix it. However, i'll try another way to find players head.
IF YOU STILL HAVE PROBLEMS
Go to your Mods/Config folder, and remove "Headlamp" folder. Then try to rebind hotkey to another button.
If still nothing, try to remove other mods and tell me if you have problems.