the pls goes rung by rung and changes bits in the output bit tables according to what is there, then at the end it will send the table to the output card and that will turn on or off outputs.
now if there is a rung later on that also has a coil with the same address, and its rung is not true, aka not all inputs are satisfied, you will be setting the bit in the bit table that corresponds to that output back to zero. so this rung in your picture is setting the bit to 1 but then a rung later on sets it back to zero again.
its either that, or the output is forced off, or that end is keeping it from executing those rungs