Set the Buttons sprites collision to disabled, So you can't click on it, Then when the player die set the collision to enabled, Now you can click it.
In the the event sheet make this :
On start of layout-------set the buttons collision to disabled
When the player die-------set the buttons collision to enabled
You can set the buttons to invisible then when the player die set visible.
Set the opacity to 0% then when the player die set the opacity to 100%