Hey there,
BLZBNTAGT00000841 is a permissions error. It pretty much means something on the system is interfering with the update agent’s ability to obtain data from the patch/update service or is preventing it from applying that data to the affected client. (Be it the Blizzard app itself or a specific game client.
Moving the game to a different folder as mentioned by Theasnext could help if the issue is folder permissions related but make sure you do not move the game to an external or networked drive and make sure you do not move the game to a restricted permissions folder like Windows, Temp or even the Battle.net Desktop Folder itself.
Outside of that you have done most of what we would suggest though I want to add a couple more steps just in case.
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 intefere 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.
From here we need to manually clear the Battlenet Desktop Application and all supporting data from the system. This will not remove existing game clients.
- Open file explorer/file manager (Right Click Windows Start)
- Navigate to the folder where the desktop application would normally be installed. Delete that folder if it exists (usually program files x86)
- Type the following into the address bar (not the search bar): %APPDATA% and press enter.
- Delete the Bnet and blizzard folders inside the appdata folder if they exist.
- Repeat steps 3 and 4 with %PROGRAMDATA% %LOCALAPPDATA% and %TEMP%
- Empty the recycle bin.
- Now reinstall the app to the C: Drive.
Create a new administrator account: Creating a New Administrator Account - Blizzard Support
Once the account is created, shut down the computer, wait 60 seconds, restart, log into the new profile and try the app/client.
If that doesn’t do the trick we may need more system specific information to assist and the best way to provide that would be to submit a direct ticket with attached system files. You can do that by pressing the support button at the top right of this page then choosing contact support. The form will instruction on how to gather the necessary data.