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If you can move the wiper by hand most likely the wiper arm has just come loose. Does the passenger side wiper still work?
Ok, so that means the problem is probably in the mechanism that holds the wipers to the wiper motor. In the parts catalog it's known as a wiper transmission. If you remove the cowl to access the wiper transmission you will likely see that one or both of the arms is disconnected.
You will most likely need to replace the entire arm assembly (wiper transmission). I don't think they sell just the arm or the plastic clip.