For some powers that aren't a good fit for my class, effect doesn't show. Example follows (I am a shaman; ability shown is for a paladin).

Addon functionality doesn't seem to be affected other than the tooltip failing to display what the power does. I don't know whether it's an issue with the addon or whether the game is just failing to send the data.

Hi, unfortunately there's not much I can do about that. If it helps, any Anima Powers that display that line just mean that it's one of those that unlock a new talent for that class. If that other player were a Shaman, you'd be able to see what the power does if it was one that gave them new Shaman talents.

You can see here on WoWhead that it has the same issue: https://www.wowhead.com/spell=313840/highlords-gift
If you check the boxes for the various Paladin specs the tooltip changes, and if none are checked it will only display the same line as your image.