I started the new project, have just one track peaking at -7.2  .  It goes straight to master and it peaks at -0.5 .  All the faders are at 0, no effects in a bin,  nor PC modules, nothing. Why is there so much more gain at master?

Is ProChannel enabled or disabled?
Maybe a compressor or equalizer is on.

Are any plugs' gain control settings adjusted to increase output? I believe that would do it and the increase wouldn't show as being done by any track or bus settings.

It is possible that within the signal path that a -7 becomes a -3 because ??  
I'm not near my DAW but I'd be curious to run this test.
 
Ceate a blank project.
Insert a Master buss 
Insert an audio track  output to the master and record a test tone @ - 8 db steady. 
Leave the track fader at unity and observe the Master buss level. 
 

The point is nothing is on. I checked thoroughly. Or maybe something is very very deep ...

Now I'm interested. Granted I was mildly interested before 😉.

Have you checked nothing has gone astray in offset mode?

Jean
Have you checked nothing has gone astray in offset mode?

Please explain "astray"

Hi Afrodrum,
Apologies for not being clearer.
When there are volume (or pan, or anything) readings giving unexpected results, it’s always worth checking that nothing has been altered in offset mode. I can’t remember what the button looks like and I’m not in Sonar just now, but you can look up ‘offset mode’ in the help section.

I had a similar issue in the past when opening old sessions from a previous version of Sonar into the latest version of Sonar Platinum. Once I turned the tracks gain knobs off of zero and back again, the track volume was back to normal. After re-saving the session, everything stayed properly working.