If an error occurred during meiosis and no chromatids separated, one daughter cell would get a extra set (or two if this happened in meiosis I). This would lead to gametes with one or more extra sets of chromosomes, which would then produce polyploid offspring after fertilization.
Work Step by Step
Review Ch. 13 and see that errors can occur-- look up aneuploidy. Imagine if that happened, in terms of non-disjunction, for an entire set of chromosomes-- a gamete which was more than n would result. This, in turn, could lead to a polyploid offspring.