Update--After thinking it through, I believe that I must have leaves clogged in my skimmer line, since I vacuumed directly into the skimmer hole without something to catch the leaves. Consequently, the main drain and second skimmer pipes can't send their water because all three pipes converge into one line that enters the pump. Unfortunately, the skimmer line I used is the final one to enter the pump. So I am imagining a clog of leaves near the pump entrance that is blocking everything. How would I get it out?