Welcome to TF!
There’s a number of things that could be, but others who may have experienced your specific problem may be able to add something more useful.
I’ll get the easiest thing out of the way, even though you’ve likely already done it, which is playing something on Youtube to make sure your audio is indeed working first.
If it is, reread Koichi-sama’s instructions and make sure you placed the folders in the proper locations as described. Also try hitting the audio icon at the type, so it repeats the audio, and adjust your sound to make sure you have the volume loud enough.
Maybe others could shed more specific light… ^_^