Without seeing more diagnostic information it is hard to ascertain the problem exactly. Off-hand, it seems like its probably one of a couple things:
(1) Are you certain \libs is in your library include path (Properties->Linker->General->Additional Library Directories)?
(2) Did you possibly do it for the wrong target (e.g. release instead of debug)?
(3) It sounds like you shouldn’t need to, but do you need to add “python39_d.lib” to Properties->Linker->Input->Additional Dependencies ?