Welcome to the forum!
I don't clearly understand what you're doing or what your goal is. But for my current best understanding, it could have something to do with layers, if any of the layers are locked. That prevents the objects on that layer from being selected.
But if that doesn't seem to be the problem, please tell us what you want for a result, and step by step, what you're doing in Inkscape.
I assume what you want for a result, would be a file with individual PNG images, of each object on the canvas.