These websites may be blocked by your ISP or by WiFi router settings.Connect your ISP directly to your PC and see if you can connect those websites, if there isn't problem then probably it's router...

+1 for PureVPN, honestly I haven't used it for router but their app and service is quite good.

You should try connecting you pc directly to modem/cable to see if it still occurs because it looks more of a network problem than router.You can still try router reset, it may help after all.