Audio format issue

I have been working on some songs I made several years ago and found some issues.
 
I try and put a melodyne edit on some of the clips and it goes through a process but does not put the melodyne edit on the clips.
 
It is as if the clip is in some unknown format that melodyne cannot read.
 
I tried to simply raise the gain one DB on the clip and melodyne still would not put the edit session onto it.
 
I tried moving the clip to a new track, that did not work, I tried bouncing the clip in place that did not work.
 
I finally dragged the clip to my desktop and then deleted the clip in my project and replaced it with the clip on my desktop.
 
Finally melodyne created an edit session for it.
 
Well I have my work around but does anyone know why this happens to older projects and what might remedy this rather than having to re-sample the clips?