Need help with phone socket for adsl.

[Stellaguy]

Hi guys. I'm new to this forum so hopefully I'm posting in the correct area.

The problem I'm having is with my router on an upstairs phone socket. When I connect my router to the main adsl/phone socket at my front door (built in filter) it connects without an issue but if I connect it to any other socket in my house the status light remains red and it will not connect to the Internet. If I connect a phone to any of these sockets it works fine and so the sockets are functional apart from Internet access so I'm assuming it must be the way they are wired up. I am using a large gaming tower for my pc so and it is situated in an upstairs bedroom so it is not practical to move it near the router which is downstairs so I have no choice but to connect wirelessly. However due to the distance between the two the signal is very weak and constantly disconnects. I have a phone socket right next to the pc so if anyone knows how I could get this socket working with my router it would be much appreciated.
Thanks.