While you can tell me that you are also conscious, and you can try to communicate to me what it is like to be you, I can never have any direct experience of anyone else's consciousness, and I know of no instruments or experiments that I can use to study, or even confirm the actuality of, any consciousness but my own. It is, that is to say, difficult to conceive of any proof that solipsism is false. So we will consider, without choosing among, a number of possible answers to the question of which objects or systems in the universe have subjective consciousness. This is a rather radical thesis, but perhaps not as radical as it appears at first glance. It has little or no impact on physics, for instance, or on much of anything else except perhaps morality.
Solipsism has some hard problems to solve.
These can be treated as challenges, though, rather than objections. Essentially everything in the universe is conscious. There are many forms of this answer. This evidence is by no means conclusive, of course. Again, these results are not necessarily fatal to the theory, but they are themselves problems to be solved.