A discount code in a link was always applied, and the total due was always right - but the order summary showed the full price on the plan line and again on the selected billing period, with the discount itself a few rows further down. It was easy to glance at the page and conclude the code had not worked.
The summary now opens with the offer: the price with a line through it next to the price you are paying, the code that did it, and what you save. On a phone, where the summary starts collapsed, the struck-through price sits in the bar alongside the total. Change your billing period and all of it updates with the price - including disappearing, if the code does not cover the period you switched to.
The discount line in the totals is also easier to pick out now, and the refund note is shorter.