The addon wont show properly or at all once the game version is no longer Classic WoW.

I kinda fixed it by replacing row 12 with
Constants.ENV = "classic" from Constants.ENV = "retail"
and commenting lines 14,15 and 16 in file constants.lua .

I dont know the propper WoW project nomenclatures so i cant properly fix it but this example does the trick.

This also worked for me in WOTLK. Thank you. Maybe someone can fork this and re-release it?

local WOW_PROJECT_CLASSIC = WOW_PROJECT_WRATH_CLASSIC

3.4.1 and the new API seems to have broken it. Any idea how to make it work ?

Sadly the developper has stated that there's no classic version and never will be...
Also taikokii suggestion doesn't work anymore.

Not playing classic ATM, tried with @taikokii suggestion?
BTW: as far as i know this project was abandoned. Somebody updated it but only for retail. Might be worth asking there for a classic version.