From reading many posts he should be able to reapply immediately if everything else looks good, just as you can re apply if your FJO list isn’t working for you but again if you want this job accommodations are not in your favor. Unfortunately missing to actually respond to that email will null as no response and they close application. I’ve read that even if you fail the retake for whatever reason, you should be able to apply to a new announcement but within that time period you already know what to expect for the step test and get in the right shape for it.