I've tracked some vocals in a project that needed some Melodyne fixes.  After butchering one of the phrases of one of the clips that needed pitch fixing, I gave up.  I thought I'd import the original(take/clip) wav file.  After importing the original wav to the existing vocal track, you can not hear anything.  However if I import that same clip to a newly created audio track it plays fine.  Tried to drag that same file to the existing vocal track and it again can not be heard.  Side note, I also can not drag/drop an wav or mp3 into the project.
 
Sonar Platinum Version: 23.1.0 Build 32   

Interesting...I just bypassed the FX rack and the vocal wav import works.  However if I turn the FX rack back on, which has melodyne, it won't play.

Just use UNDO, That's how you back out of a sh!t pile.. It won't work if you closed the program but UNDO is your friend.