I made a UI in the new canvas system.
The canvas is placed in the Menu screen and made into an Unity-Singleton with DontDestroyOnLoad(true). The canvas uses the “Screen Space - Camera” option.
While in menu screen everything works perfectly - the buttons get highlighted when hovered and can be clicked.
After loading a new Level the buttons do not work anymore. They don’t react on hovering or clicks.
There was no change done to the canvas while switching the level and I have no idea what is causing this trouble.
EDIT: I found a fix: somehow there was no eventsystem attached to the canvas, adding this made it work.
But I still want to know why. Why does it work without the eventsystem in the first scene and not in the second one?