Hello,
Maybe somebody can help me figure out why this happens.
I installed a vpn (not turned on) and then I get instant disconnect when I type in my password.
When I deinstall the vpn, it is back to normal and I can log in.
It is pretty obvious that the vpn does something to the system that doesn’t interact well with wow.
Does the VPN software have some sort of “Kill Switch” setting?
No it has no kill switch.
If it had thought, wouldn’t it also mean I had no internet access?
Also my battle.net is connected but I just cannot log in.
Meaning I can even chat with friends through the launcher and it shows I am online.
But once I press on play and the game starts, it immediately disconnects
Be careful when using a VPN with WoW. You can get detected wrongly for “account sharing” or “account compromised” and have a very hard if not impossible time to get the account back! Been loads of reports of this happening over the years. 
I always turn mine off to play WoW just to be sure.
nah, I m not using the vpn to play.
My account got auto locked several times before because I travel between 2 countries and log in from 2 different locations.
So I told the support to remove that auto lock from my account.
So far nothing happened anymore since 2 years.
problem is just the vpn is installed and offline and I cannot log in, while internet etc. works.
If I uninstall the vpn, it is back to normal. I would guess there might be something with the adapters but I also tried to disable the vpn adapter without any result