How to make when click on button in the 3D Widget was activated Matinee animation?
Depending on where you are creating the widget you need to use event dispatchers and assign that event to play the Matinee in level BP. You can find an example in this project: [FREE PROJECT] Physics Driven Spacecraft - World Creation - Unreal Engine Forums
Level selection button activates an event dispatcher > that activates another event dispatcher in Player Controller BP(since the main menu widget is created in player controller BP) > then finally in Main Menu level you get the player controller > cast to playercontrollername > bind event dispatcher to play the matinee.
Edit: Didnt notice that you are using a 3D widget. The process is the same anyway. You just ned to get a reference to your widget to get to the event dispatcher.