Assuming it was a queenless split, about 1 month after the split you should be seeing eggs. If there is still good numbers of bees in the hive give it a frame of brood from one of your other hives. It could possibly do with the extra bees, see if they start to raise q cells.
Do they seem queenless? That is are they stirred up, racey, a little jumpy crazy like. (Hard to explain until you know it).