Oh no! I'm so sorry Kate! So, we had this happen to us a few years ago in an older house (not a new construction) and I don't know if this will help you or not, but at least I can provide some info on what happened to us. We had a particularly rainy year and basically, the soil around the house was not completely compacted so the water completely soaked the soil, eventually leaking into the basement. There's actually a great video explaining this here: https://www.youtube.com/watch?v=QlUZwwKDqXo
We ended up hiring a waterproofing company called B-Dry which has a lifetime warranty on its products (we have actually now demanded that this be done in all of our future homes --- that was 2 homes ago, and we've now gotten B-Dry to come in on our last home and our new construction house). They created a French drain system for us with a channel into a sump pump and then they waterproofed the entire basement area of the home. After dealing with water in my basement, I swore I'd never deal with it again because it's such a headache and heartache.
I would want to know if the water is coming in through the floor or if it's coming in through the windows. If it's coming in through the windows, it's a much easier fix than if it's coming through the floor. Also, take as many videos as you can. One of the issues that we ran into is that our insurance company refused to pay for anything --- in your case, your new home warranty should cover the costs, but I would push to get a real waterproofing company to come in and fix all of this.
Q