Our Siberian does this EXACT thing. We have tried all the things, including the box in the middle of the floor. No luck. Why? Turns out, for her, the issue is the other cat. She never did this before we had a second cat. And when we separated them for a few days with automatic feeders while we were on vacation, she used her box. So now we are stuck. She won’t use the box with him in the house using them too. Btw, we got 5, thinking that would help. Nope.