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Try plugging the dsl connection directly into the phone socket assuming you are using a splitter, or it could be a fault with the dsl cable the cable might be damaged somewhere, just some suggestions.
I have connected it directly into the socket but nothing, and I thought maybe the cable might be faulty so tried 2 other cables but the same story unfortunately
Could you send me a private message (PM) with your landline number so I can check this for you? Just click on my name then click on "send me message".