When I'm trying to cut extrude, there are points touching 2 opposite sides of a rectangular block, talking about the top view, I can't cut my object out. How do I extrude cut it?

I need help trying to extrude cut. Question: When I'm trying to cut extrude, there are points touching 2 opposite sides of a rectangular block, talking about the top view, I can't cut my object out. How do I extrude cut it?

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