I cannot sync new playlists from iTunes PC to my iPhone

I have read through many Apple support topics and how-tos, I have tried everything I can to get iTunes to copy over/ sync new playlists from my PC. Doesn't matter if I select manual choosing of music, or select individual playlists, update my preferences, or drag the playlists over to the iPhone... every single time I try syncing the result is that those new playlists NEVER APPEAR on my iphone. I do usb syncing, wifi syncing... nothing will work.

This is incredibly frustrating!! Now I understand why so many of my friends are just giving up on Apple products.

Why does such a SIMPLE process not work???