I just burned 3 DVDs. They all play fine on my TV/Commercial DVD player, but when I open them on my PC (Windows Media Player and Media Player Classic Home Cinema) they just open up to the Files currently on Disc menu... so the client can't play on their computer.
On my computer, I have to open the DVD software first and then open the DVD through that interface. If I try to open from the DVD first, I get just the files as you described. If the client has their software set to Auto Run when a DVD is inserted, that should do the trick.
I am sorry, but I don't have any ideas why it doesn't work. I have created dozens of DVDs in DVDA and they all work on computers and DVD players. Good luck.