A few things happened. There were permitting delays at first which pushed back the start of construction, then rain caused some major problems right at the beginning, and then several of the suppliers of equipment had delays. For instance, the fountain manufacturers had some issues with the equipment at first that set them back. Then the lagoon itself had some structural problems and wasn't keeping the water level where they needed it to be. So.. a lot of stuff.
What I heard recently is that the show will most likely open without a few effects in place and those will be added in the following weeks. They'd rather have a show open before September than wait for everything to be installed permanently.