In principle, it could be the case that although materialism is true, there is some class of physical systems that can't be simulated on computers and this happens to include the human brain. In principle, it could be the case that the human brain could be simulated on a computer but is is impossible for anybody to understand the relevant algorithm and so impossible to set up the simulation.
In practise, the first possibility is ruled out by the best existing theory of computation, which states that any physical system can be simulated by a universal computer operating by finite means:
The second possibility seems implausible. It has to be the case that whatever algorithm our brain is running was created by rounds of variation and selection such that each stage it produced something that allowed genes to be copied. So there must be some sequence of problems we could solve that would lead to something that could be tested at each stage and would produce AI at the end. Why would we be unable to do this? It can't just be a matter of memory or speed or reliability of computations since computers can do that for us. So I don't see what can stop us from creating AI.