Authentication FAIL

[#1]

I have a thomson router which until recently worked fine, conducted the online self help, but my router still shows authentication fail.
When i open a web browser it points me to the thomson gateway, have tried authenticating under guidance from plusnet advisors but still no joy.
During authentication the INTERNET light on my router will flash green, solid green then turn red, then no light.
I have tried a different micro-filter and even hard wired my laptop instead of wifi, only thing left is a different router, which will be checked later this afternoon
ALL OTHER LIGHTS ARE SOLID GREEN

[#2]

Hi xxwardyxx,
thanks for your time on the phone. As discussed I'll call you later this afternoon and we'll be able to perform some diagnostics.
Jojo

[#3]

@xxwardyxx
I tried to call you on your mobile to follow this up but as soon as it connects, it just goes dead. Also tried to contact your landline but it just rang out.
I've contacted our counterparts at BT who have made some changes to your line which they hope should enable you to reconnect. Could you please reset your router and then reconfigure it and let us know how you get on. Thanks.