Which router and operating system are you using please?
How is the router connected?
To eliminate any wiring problems in the house connect the router directly to the master socket by carefully unscrewing and pulling off the lower cover (careful of the short wires) Plug the router through a filter into the socket.
Try and connect now. If this does not work the next thing to check is that the filters are working, see if you can borrow a spare one rather than forking out first.
These are the checks to do from the described problems...