My game patch is 8.1.5.29896 and I downloaded the latest addon version. (version 8.1.2.)

For me, Pet Tracker does not show up in the addon list within the game. Resulting in that I can't use the addon in game.
I put the addon in the map where I put the addons I'm using successfully, so I don't think the placement is the issue. But I don't know, and can't find online, what does is the issue.

(I did found that sometimes you need to drag some files out their maps within the addonmap. However, doing this didn't make a difference for me.)