So I have a vanilla version of Arma 3 installed and it runs fine if I upgrade it to Dev it will open and load the Tanoa map fine.
But when using a Dev build installed parallel using the Arma 3 Tools and updater I can use All apex content but the Tanoa Map.
I've verified a few times now but it just gives the "Please switch off the game, wait until steam downloads the DLC and start the game again" when I attempt to open the map in the editor

If its not Obvious I do own the Expansion already. Not sure if tools is the category or not.