105, welcome to the forum!! Matt and Dave are right about the possible problem if the skimmer line is the only working line.
Does the skimmer have 2 ports? - some morons plumb the MD through the skimmer and use a special attachment in the skimmer to regulate the flow of the skimmer and the MD If you're not sure just see how many lines come up into the pump - if it's only 1 the MD is probably plumbed through the skimmer and you'll need the special attachment to get any water movement through the drain.