I don’t use that specific model but something similar. Somehow air is leaking into it and breaking the suction. It could be a bad fit on the O-ring or a damaged O-ring, there might be a leak at the top where that black fits to the white, or it might have a pinhole somewhere. Another common problem is that if it is not setting pretty level the water can just run out. That can also be a problem if you try to hang some waterers that depend on suction like that model.
If you had it setting level where the opening at the bottom was covered with water and it still leaked out, I’d take it back for a new one.