After months of frustration stuck at ".... Checking one more thing..."
Finally tried going into my router settings and changing my DNS servers to Google's public DNS - 8.8.8.8 and 8.8.4.4 - it worked !!
On my router this was under Internet Connectivity / IPv4 , where I changed from "Obtain DNS Automatically" to Manually Specify DNS" and added 8.8.8.8 and 8.8.4.4
The Microsoft Troubleshooter guide only mentions Wireless Isolation, i.e.
"Many routers have a Wireless isolation feature that allow you to lock down the network. If this Wireless Isolation (or AP Isolation) is enabled, then all devices connected to the Wi-Fi network will be blocked from communicating with other".
My router had nothing about wireless isolation or AP Isolation - suggest Microsoft adds some troubleshooting advice on DNS settings for Your Phone.