Either the points or a wire is shorted or the points aren't making good contact, depending on the configuration of your continuity test setup. Points can close, but have too much resistance to conduct any significant current, or a wire can be broken or unplugged under the tank, any of which will give you an open circuit. Points can have the screw that connects the wire misassembled and shorted, wires can be frayed and shorted, etc., all giving you a constantly closed circuit. That doesn't count possible, but unlikely, condenser problems.