Problem Setting up TP-Link AC1750

[#1]

Hi npr,
I did try and connect directly to the modem but it would not connect, it just kept say no internet 

[#2]

You plugged the long ethernet cable in to the modems No1 port and the other end in to the PC ethernet port?
Those instructions do work, but it could be Norton interfering with the connection.
Is there a setting in Norton to disable it for a while or better still are you prepared to remove it?

[#3]

thank you for your patience,
I'll have another go at the weekend.

[#4]

Hi Guys,
Here's an update, I have now removed Norton and the internet is now about as bad as it has ever been.
As an example I have open a new tab and in Google typed Speedtest and google returned a search within 0.31 seconds, I then clicked on Speedtest.net and the page has still not opened in the time is has taken me to write this message. 

[#5]

Is the PC accessing internet okay when you revert to a wireless connection ?
What make/model router were you using on fibre prior to getting the AC1750 ?  (Plusnet TG582n ?)
Can I suggest you install the old router and check the internet connection via ethernet is working ?

Other thoughts:
Is the firmware on the AC1750 up to date?
Is there a newer Realtek gigabit driver for your PC, via Windows Update, may be listed as a 'optional' update?
Do you have another PC or laptop which you could hard wire to the AC1750 to test because it is not at all clear where the fault lies  (ie. PC or router)?

Update:
What is the full model no. of your AC1750?   Is it an Archer C7 v1, v2 or v3 ?
I found one similar case on TP link forum with slower than expected LAN connection:
http://forum.tp-link.com/showthread.php?79516-Archer-C7-Slow-LAN