They are a bit finicky and have a tendency to do that whenever something disrupts the surface tension of the water. I had an Aqua C Urchin Pro for a couple of years which would do the same. Most skimmers will either overflow or the foam head will just crash during a water change or if something oily is fed to the tank. Once things equalize and get back to normal (usually after an hour or so) it should return to working normally.
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