Update , I went in again with what you said in mind and found the Merge option , I used Forte as my DXi on all instruments and did an experimental merge , got a message saying ' Some tracks are not assigned DXi , and will be silent ,do you want to assing them the default synth? -

I gathered that any track with no synth had no sound so I said no , chose Merge and it succesfully sent out a wav file , but on openingthe wav it was silent , what am I doing wrong ?