I keep getting error code BLZBNTBNA00000012

Limitations with Blizzard Support for Activision titles.
In regards to Activision, we only handle the distribution of the game client for Activision. We will assist with anything related to the desktop application and anything with the game client that involves purchasing, activating, downloading/installing and launching. Anything that occurs after you can press the play button is going to be addressed through the Activision support portal: Support Options | Activision Support

Now the specific error indicates a corruption or permission issue between the Desktop Application and the game client. So the following steps should help rule out any potential issues with the desktop application itself.

Try doing an extended power cycle on your system. Turn off all devices including the modem. Wait 30 minutes, turn on the modem, wait 5 minutes, turn on any network devices, wait 2 minutes, turn on your computer and try the game.

You can try switching your DNS settings to use a free public DNS servers instead of your ISPs Servers:

We do not have individual steps for specific modems or routers so if you need assistance accessing or updating the devices, contact the device maker/provider.

Sometimes firewall or routing software/hardware will have some advanced settings to prioritize and manage types of network traffic. Normally that is not an issue but we have seen situations where it can interfere with the delivery of the data for our games/voice chat.

Let’s try turning off these features:

QoS
SIP ALG
RoG (ASUS Routers Only)
Security firewalls (Some ISP provided modems)

Not all devices will have these options and the steps for turning these functions off will be different depending on the make/model/software version of the devices and programs involved. If necessary look at the documentation for your security and routing products to find out how to turn these options off.

In some cases there is a corrupt or misconfigured setting within the router or modem. We cannot say what that might be offhand but the easiest way to resolve these conflicts would be to factory reset the router and/or modem.

You may need to look up your specific model for the steps on how to do this and in some rare cases you may need to have this done by the ISP. Feel free to reach out to them for assistance if necessary.

Try running your system in selective startup mode: https://battle.net/support/article/200483

We need to not only remove all data relating to the Battle.net Desktop Application and affected game client, we need to ensure we have good permissions for reinstall.

  1. Launch the Blizzard Desktop Application and select the tab for the game you need to ensure is uninstalled.
  2. Is there a settings button (gear symbol) next to the install/update/play button for the game? If yes, click it, then choose show in explorer.
  3. If there is no gear symbol, right click Windows Start, choose open explorer and navigate to where you would have originally installed the game. (typically under Program Files(x86))
  4. If the uninstall option is available use it and then manually delete any remaining folder/files for the game in file explorer. If there is no uninstall option, then manually delete the game folder if it exists.
  5. Leave the explorer window open but exit the Battle.net Desktop Application.
  6. In File Explorer, navigate to the folder where the desktop application would normally be installed. Delete that folder if it exists (usually program files x86)
  7. Type the following into the address bar (not the search bar): %APPDATA% and press enter.
  8. Delete the Bnet and blizzard folders inside the appdata folder if they exist.
  9. Repeat steps 3 and 4 with %PROGRAMDATA% %LOCALAPPDATA% and %TEMP%
  10. Empty the recycle bin.
  11. Create a new administrator account: Blizzard Support - Creating a New Administrator Account
  12. Once the account is created, shut down the computer, wait 60 seconds, restart, log into the new profile.
  13. Now reinstall the app to the C: Drive.
  14. Reinstall the game client.