UMG buttons not responding

Hi, when working on my class project I encountered a problem. I created a Main Menu to select a few different 3D models to view. To do this I used buttons that were supposed to open different levels. At first they lagged like crazy and now they stopped responding at all.

I know that the buttons are pressed because they go from grey to yellow but nothing else happens. I can also press all the other buttons like options and quit but like the other one they do the same thing.
This issue only occures in the main menu level. The pause menu I set up works.

UMG problem - Album on Imgur my blueprints