New router arrived today and problem solved! Thanks for all the help and hopefully this tale can assist others.
I have brand new Inspiron 5559 running Windows 10. It connects to my wi if and says it has internet access, but I cannot open any websites. My connection is fine and works with 8 other devices, although none run Windows 10. I ran the troubleshooter and got the message "one or more network protocols are missing on this computer".  The detail message says "Windows sockets registry entries required for network connectivity are missing".  I have most of the solutions suggested on the Microsoft site using device manager and command prompt, but no success. It did briefly connect for a few minutes but then failed again. Has anyone any ideas? I suspect it's something to do with Windows 10 compatibility with the hardware? But it's a new machine supplied by dell.
Network protocols missing. Windows 10