Two canvas in a scene, but the newly created one doesn't work.

I have two canvas. One for the congratulatory finish screen and the other one for a pause menu. While the first one works properly, the second one doesn’t. Moreover, it doesn’t do other operations I had assigned it to do, such as freezing the game to look like its paused and the pause menu showing up.
The pause menu Canvas doesn’t even show up in the scene view.

Is there a way to fix this, or could it be that using two canvas in a scene isn’t gonna do great?

Canvases are rendered based on z position property.
but i would say if you are talking about overlay canvas you really need just one. And then enable disable child components. I use one overlay canvas and many others in world space.
but that said. You can have more than one canvas. You say you are having issue with script assign to it. Which does not matter what the gameobject is. You have some issues there more likely.