Where are you located? It's late for swarms here in North America, but not unheard of. The first question is why they swarmed. I assume you harvested and crowded them down, or you live somewhere else where it's "spring" now.
Why do swarms abscond? Who knows. Sometimes you didn't get the queen. Sometimes they just decided they didn't like the accomadations. I like a few drops of Lemongrass essential oil in the box to anchor them there better. Some open brood (which is not available here right now) is also helpful to anchor them to the box.
If you're resonably sure you have a mated queen (based on her size or her being marked) you can put an excluder on as an includer for a week or so, so the queen can't leave and that tends to anchor them.