UI not working after build

I'm using Unity 2019.3.10f1 on Windows 10. I have 2 scenes in my game, the level and the main menu. When I run the game in unity it works although both scenes are running at once, so I can control the player in the menu screen. The main problem is when I build the game, the UI gets all messed up. The buttons no longer work, they don't even change when you hover over them, the text is moved closer to the middle, and the health bar in-game is also in the wrong position being moved closer to the middle. I've looked around for ages looking for a solution but I can't find one anywhere.