If no telephone will work when plugged into a certain phone receptacle--but the phones work in other receptacles on the same line--assume that either the modular phone receptacle is bad or the wires that connect it to the rest of the system have become loose or severed.

Open up the phone receptacle and look for disconnected wires--ones that have insulation stripped from their ends but are not connected to terminals. If you don't find any, buy and install a new modular phone outlet. For help with this project, see How to Install a Modular Phone Outlet.