With 728 solo plots, his expected time to win is 4 months (https://chiacalculator.com/). It is fairly common to be “unlucky” and wait more than 300% of expected time to win before hitting a block. See flexpools historic % luck as a good example for how frequently this happens (Notice of Closure). There are also several examples of this level of “unluck” in this forum (me included, see No rewards for 9863 plots for about a month for some inspiration).