The tick is the light that tells you if the router has got a connection to your ADSL, if that is going out then you either have a problem with your phone line or the phone wiring in your house.
I'd agree with the "local expert" that an easy first thing to try is changing the filter, the filter is a little box that will be plugged into your phone socket and then the router is plugged into that, you probably got a couple with the router so try changing it for the other one.
As for running it from a different phone point, they are best connected to the main BT master socket, so if it's currently plugged into an extension socket you may get better results by moving it to the master socket.