The VPN servers may be down temporarily. Make sure you're not using a free VPN as they have the lousiest servers that will literally drive yo up the wall. Believe me, I've used HotpotShild and CybrGhost so I can really write a whole book on that. I guess you could try some of the leading VPNs out there as they rarely have such technical problems. I'm currently using Ivacy VPN which is fast and user-friendly. The 2-year subscription costs just $1.66 per month so it's really easy on the pocket.