F5 appears to work, as does Command+R.
If you are on a laptop, perhaps the shortcut key functionality (volume up, volume down, etc) keys are taking precedence. To correct this you can hold the fn key while pressing F5, or by changing this preference in System Preferences > Keyboard & Mouse.
If you are on a laptop, perhaps the shortcut key functionality (volume up, volume down, etc) keys are taking precedence. To correct this you can hold the fn key while pressing F5, or by changing this preference in System Preferences > Keyboard & Mouse.