Do you have a software firewall running on your laptop? If so, try disabling it temporarily to see if that makes a difference. Do you have a Killer WiFi card? I recall posts about it blocking access to certain web sites. IIRC, some settings needed to be changed. Try opening Killer settings and disable Killer prioritization engine.
    I have a brand new XPS15 9510. My issue from day one is that some websites, but most noticably web.whatsapp.com will not load after the laptop comes out of standby mode. This problem identifies itself in different ways:- No QR code loading- ERR_CONNECTION_RESET message- TimeoutsThis occurs in any browser and only on this laptop. Things I did in an effort to resolve:- Updated all drivers- Tried different browsers, laptops and DNS settings- disabled MIMO power save mode in the wlan adapter settings   Any help or tips is greatly appreciated.
Certain websites not loading, after reboot all ok