Minecraft Launcher login connection problem

So, I use a VPN/Proxy to play sometimes, because my internet blocks Minecraft servers. A few months ago, I was able to play normally, but some weeks ago I found a bug.

I can login without a VPN activated (but I can not play multiplayer, only singleplayer). Printscreen: http://prnt.sc/eau7yk

But if I turn a VPN on (to be able to play multiplayer) using THE SAME PASSWORD OR USERNAME that I used before a screen appears saying that my username or password is invalid. Printscreen: http://prntscr.com/eau9v8

I tried three VPNs and the same thing happens.

What I expected to happen was...:
The game log in.

What actually happened was...:
A screen saying that my username or password is invalid.

Steps to Reproduce:
1. Turn any VPN/Proxy service on
2. You will not be able to log in to your Minecraft account
3. Turn any VPN/proxy service off
4. You will be able to log in to your Minecraft account