Why are my UI buttons in Unity not interacting with the mouse pointer?

I was making a Tower Defense game, and I hade made an upgrade UI, all I had to do was change it from on hover over the tower to on click. I made it on-click, and it worked fine, until later. All the buttons just stopped working, but ONLY in the upgrades and sell UI. The hover effect doesn't even work anymore.

Here's what I have:

• A Camera assigned to the Canvas seeing as it is world space.
• An EventSystem.
• Interactable and Raycast Target enabled on the buttons, but nothing else.
• A Graphic Raycaster, a Canvas, Canvas Scaler, and a Canvas Group on the Canvas.

Here's what I have tried:

• I have tested the EventSystem for registering the PointerEnter and PointerClick, no results. It's like the buttons don't exist.
• Moving the buttons outside of the Panel.
• Deleting the Empty GameObject that was a parent to the Canvas.
• At least four questions on Stack Overflow.
• At least two questions on Stack Exchange.
• At least six questions on the official Unity site.
• At least two videos.
• AND I DID EVERY SINGLE TRICK IN EVERY SINGLE ONE OF THE ANSWERS.

Here are some screenshots of things in the game:

The Hierarchy in the Scene:

The Hierarchy in a tower:

What the tower looks like:

The EventSystem being unresponive with the buttons:

Button config?:

Debug.Log(EventSystem.current.currentSelectedGameObject);

Result:

null null null null null null null null null null null null null null null null even when I click on buttons that work.

Ask me if you need any other information, just ask. I'm getting extremely desperate.