What is the proper CV listing for an accepted paper that was not presented? This question is similar to ones about accepted papers not being presented; however, one thing that other answers fail to mention is how to list the paper in your CV. Quite simply what is the appropriate way to list an unpresented paper where you are are a) solo author, or b) a co-author?
The paper does appear in the proceedings


Its appearance in the proceedings makes it a publication, so you can (and should) include it in your list of publications.

If you separately list your conference presentations, you can't include this paper in that list, because you didn't present it.  Similarly, if your list of conference publications indicates which papers you presented [for example, by writing "(presented)" or making the presenting author's name bold], you can't give that indication for this paper, because you didn't present it.


  where you are are a) solo author, or b) a co-author?


This is irrelevant.  The publication list in your CV should list all authors of each paper, ideally in the exact order they appear on the paper's title page.

tl;dr: Just tell the truth.