No problem. Thank you for the additional information.
I’m going to assume when you click start game that the sound and the particle effects play. I’m also going to assume the name of the level in open level node is correct.
That being said if it becomes unresponsive, it sounds to me there is something wrong with the actual level, or the level is simply to heavy to load all at once. How long do you wait? Will it eventually load if you wait long enough?
I would say instead of opening the level in one whole pass like this, you should be loading the level in stages behind the scenes and with streaming volumes. So even though the player is at the start game menu, you should already be loading the level. (Actually you should be loading the area the player will begin in). Then as the player moves through the level you should be using streaming volumes to load and unload parts of the level that the player is moving into and from.
This is a good primer on level streaming by epic: Getting Started with Level Streaming | Live Training | Unreal Engine - YouTube