Seeing the audio displayed as you are recording is a function that can be turned on or off as desired. Displaying while recording takes more processing power....so the option is there to turn it off. 

Midi, when recorded, will not display audio at any point until the synth is frozen or it's bounced to track or clip. 

be sure the midi tracks are set up properly and the track is armed. The red record button needs to be clicked on, and the track itself will change to a shade of red as well when it's set up to record.  I rarely use the simple instrument track format, choosing to see both the midi and the audio track associated with it.... I'm old school.

I see the midi captured in the midi track and nothing is in the synth audio track. 

I have had issues in the past similar to what you are describing. Issues that were involving ONE particular project. I was not able to figure out what was happening, nor a way to  "FIX IT". 

I tried the complete cold reboot of ALL the studio gear...computer, interface...all from a cold start. Kill power, restart. 

If that fails... there is another possible thing to try. 

Start a new project. Add the tracks and then drag the audio tracks from the old one to the new one. Add your synth tracks and try with a new project.

It is possible that something in the project is corrupted and is causing things to not work correctly....or you clicked something without realizing it...... I thought I saw where this is related to one project and not the others. So copy and drag the audio in to a new project and see if that solves the problem. 

I have had to do that a time or two in the past when I had something go wrong and was not able to figure it out. 

@John - I do not know the source for the audio tracks, and it doesn't matter.  He indicated that he armed all of the tracks, and that post-record the waveform data is visible for the audio tracks, and that he can hear the audio tracks on playback.

Quoting Alex: 
 
* The waveforms graphics now appear for the audio tracks and I can hear the audio tracks - OK 


And:


As stated "All tracks have echo and record on" so they are armed.  As stated with new projects no issue (i.e. I generally know what I'm doing).  The issue is specifically to do with soft synths not recording and the record button not showing as a red colour whilst recording. It's recording though, just recording audio tracks.    
It would appear that the project is somehow goofed up internally, and that if he creates a new project with the same layout there is no trouble.

Bob Bone

Exactly Bob, spot on. That for repeating it a third time :). Folks please read my first and second post carefully! :)And as stated if I create a new project no issues, works fine. These are soft synth tracks I had the issue with i.e. Insert > Soft Synth on the main menu. We all know what this does.

I was wondering if there was some of disconnect going on. I guess I'll have to put this down to a weird bug rather than schoolboy error.

Thanks..

@Alex - As one of the other posters indicated, sometimes individual projects seem to develop anti-social behavior, for no discernible reason.  It has certainly happened to me, and after a few shots at trying to figure out if it was something I did, I just gave up and started a new projects and moved on.

On the plus side - this means you haven't used up your allotment of 'school boy errors' for this week, so you can still get some of that in by the weekend.  :)

Bob Bone