How do I get Transport to work?

Sorry , complete newbie , downloaded Ardour for PPC running OSX 10.4.11 , I’ve got Jack running and routed , imported an audio file , but the transport button just doesn’t react . Record button lights and goes out when clicked , “Shift to end of track " works ,” Highlight section of track" works , manually shift playback head cursor , everything else works but playback remains resolutely stuck . I’ve tried different playback options.
Have I missed something very basic?
Thanks if you can help.

Check to make sure you don’t have the transport sync on Internal, make sure you are connected to Jack, etc. I don’t know to many people that still use the PPC bundle so it is possible you found a bug, but unlikely.