I'm probably doing something wrong but when I try to record more audio or midi on a track that has already got data in there is no playback even though the waveform/notes are visible. It only plays what I just recorded.
 
Any ideas on what could be causing this?

Why are you recording on the same track? You can have 100's of tracks. Are you talking about punching in over a mistake? 
Anyhow, make sure all your audio and soft synth's tracks outputs are set to Master and your master to your audio interface etc. Sound like a audio signal path issue. 

You may want to check Edit>Preferences>Project>Record>Record Mode, to see what it is set to - this is a per-project setting, and can be set to: Comping, Overwrite, or Sound on Sound.
 
Hit 'F1' to pull up context-sensitive help for that dialog box, and it will explain the choices.
 
Bob Bone

Solved nice one fella, just my way of recording my rough guitar track after doing a certain parts of a song.

robert_e_bone
You may want to check Edit>Preferences>Project>Record>Record Mode

Or right-click the record button in the transport

Yeah - I thought he might find the help content helpful.
 
Bob Bone
 

Nah quality help guys still finding this daw business confusing at times!
 
Many thanks though