You have smoothed edges on the two walls that are internal. Turn on hidden geometry under view, and erase the two small lines separating the inner walls from the outer. Then it will push pull.
Yes. But it’s important to understand how you got smoothed edges which are not appropriate in this context. My guess is that you did it by accident while using the eraser tool, if you hold down the option key the eraser tool smoothes instead of erasing, don’t do that. Just erase the edge, no keys.