Selecting the correct WoW directory

While WoW is running, open your Task Manager via CTRL+ALT+DEL. In the Task Manager, switch to the Processes tab and locate your World of Warcraft process. Rightclick the process and select "Open File Location". This will open the WoW folder you actually use to play the game. Copy the file path to this folder and then make sure that the WoW directory setting in the tsm desktop app is set to that very same file path.

Once you have set up the the correct WoW directory, restart the tsm desktop app, wait for it to download pricing data and then do a /reload ingame.