If you're experiencing the "BLZBNTAGT00001389" error while updating a Blizzard game like World of Warcraft, or if you keep seeing "CAS System was unable to initialize: Tact instance creation failed" when launching the game from the Battle.net macOS client, you might have a permissions issue.
Here's how to fix it:
Solution 1
1. Open Finder, go to `/Applications/World of Warcraft/Data`
2. Move the `config` folder to the Trash. It's about 14KB, the Battle.net client will re-download it later.
3. (optional) Next, go back to the Battle.net client and run the "Scan and Repair" task for your game.
Everything should work fine after ward.
Solution 2
Open the Terminal, run the commands below.
cd '/Applications/World of Warcraft/Data'
sudo find . -type d -exec chmod +x {} \;
sudo chown -R $(whoami) .