VPN can't be connected in Windows 8 - Windows 8

Very strange problem: I have about 5 wireless routers, and I have two VPN accounts.

I can use those two VPN connections on 4 routers, but the rest one, which I use a lot, I can't connect with VPN based on that wireless router.

I don't know why, the system keeps notifying me that 619 errors. And I googled the problem, they said the settings of that router doesn't allow VPN connection. However, after I logged into options of that router, I can't find where the settings for VPN is.

Can you help me? I feel rather troublesome for I have to change my internet connection when I need to use VPN.

I have never encountered such problem. Did you detected some IP conflicts? Check it!

Or you have to check your network card or its driver.