Maybe when the dealership did the job they didn't tighten down all the bolts. Check the reservior to see if there is fluid. Check for Fluid on the floor,fluid on the floor should mean your slave cylinder is bad. Maybe if you look under the car you can look to find your master cylinder to check for any leakage there. If you don't find any problems there take it to the dealer I wouldn't think they'd give you too much of a problem if they did the work. Every once a while you hear of shops forgeting to tighten down this or tighten down that. it's possible.
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