Unable to connect to any VPN

I am having problem with connecting to any vpn configuration. I have tried so many apps (vpn express, hotspot shield, betternet etc.) but every time i try to connect either it says the vpn server doesn't respond or it says the vpn server unavailable. I have also tried deleting all these apps and resetting network setting then reinstalling these apps one by one but still nothing works. Can't connect to any vpn server. I am sure it's not those servers as how can it be that none of these vpn service providers are online. Can anyone tell me what the problem might be and how to solve it?