No other settings needed there, but Windows controls the timeout still (DisplayFusion just allows you to control the Windows timeout from the Screen Saver tab). Usually if the screen saver doesn't start after the idle time, it's one of these things:

• Some browser tab or media app is requesting the computer stay awake.
• Some device driver is requesting the computer stay awake. In my experience it's been things like wireless keyboards, mice, game controllers, etc that do this.

You can run the following at an elevated command prompt to check if something is requesting a wake lock. It won't always show the culprit but usually does:

Hope that helps!