Escape from Space

Although I am working on the game and improving the level, there is no problem, although I see my character on the game screen, my character is deleted from the scene when I build it. https://www.coursera.org/learn/game-design-and-development-2/discussions/forums/... As it is said in THIS comment, my character is deleted from the scene and never comes back. I worked on it for a day, I asked someone who knew about it and he couldn't do it either. Then my character is completely gone and no matter what I do, I can't see it on the game screen. Therefore, I installed something that shows the general level I developed. Apart from that I extended the level and introduced the mechanic of pushing the enemy. Apart from that I complexified the level design.