I had the same issue.
What I did, and did’t work:
- Clean every reference from Regedit to Battlenet and Blizzard
- Removed every file from TEMP, APPData, ProgramData, Programs x86 and Programs
- Changed DNS
- Changed internet connection
- Reset ipconfig dns from command line
Nothing worked.
Solution?
In my case I edited the host file by removing ALL the IP registered into it.
You can find the windows host file under C:/Window/System32/Drivers/etc/host
Just edit → make it empty → Save