That doesn't seem right. If absolutely nothing showed up, there is some sort of glitch. There is always something available. Or, do you mean that you couldn't get a single reservation that you wanted?
ETA: I just did a search for dinner reservations for 4 people on 6/21 and there are 37 restaurants with ADRs available.
Couldn't get a single reservation that I wanted. I don't search for restaurants that I don't intend on reserving.