I am not sure if this started today after I updated Sonar PLT to the 2017.04 build, but the audio waveform heights are a bit more work now than I remember.  twice today I recorded a few acoustic guitar parts.  3 take lanes each.  When I go to the track to comp, the comp waveform is basically a line.  I can increase the waveform so that I can see that I actually recorded something.  Then I open the take lanes, and each one of them is basically a straight line requiring resizing before I can do anything with them.  
Getting the comp parts just right, I flatten the comp.  Wave form height instantly goes back to almost a straight line.  I need to readjust and the waveform is then okay.  Doing undo of the flattening, then re-flattening repeats this flat-lining behaviour.  
 
Have I accidentally hit some key to cause this behavior?  I have 'Show Audio scale' and 'Maximize waveform' checked.  I have 'Auto Track Zoom' off.  Thanks for hopefully pointing out something very absentminded on my part.  
 
Thanks! 

So is this just a waveform display issue, or are the track meters showing low amplitude?

Now that I look, these are not very hot at all.  -22 average.  I will try to record some at a higher level, and then see what it does.  Thanks!

Recorded some takes with peaks at -9.  Still the waveform flattens significantly when flattening the comp.  Some little bumps along the line, but needs resized to see anything significant.  

What's the amplitude post-compressor?

Actually no plug-ins of any sort were being used.  So no compressor.  When I referred to 'comp,' it was in reference to making a composite of parts of several takes.  Today, I record an audio Motif 6 piano part.  A couple of tracks with multiple takes in each one in a new project.  One hotter at -8, one softer at -20.  Comping as normal, and when flattening the comp, no flat lining occurred in any one.  
 
In the old project, I got rid of the tracks that were flat lining, added some new tracks and tried the same thing.  No flat-lining.  
 
So for now, it may have just been a glitch on a couple of tracks, which weren't good any way, as my vocalist wants a much faster tempo!  And this whole exercise has gotten me much better at comping! I will let everyone know if this pops up again!  thanks!