Why is the level not properly working when I load it?

I’m having a problem with changing scenes in my Project. When I start from the main menu and press play to enter a level, the first time it plays fine, but when I pause the game and click to go back to main menu and go back to the game, the level doesn’t properly work. It works when I pause the game and hit retry though, but I don’t why it does that. Also, when the game over screen comes up, whether I click the retry button to restart the level or click the menu button to go back the main menu and back into the level it never properly runs. I don’t know what is wrong. How can I fix this?