This! Apps, by and large, are garbage. And it's not just recreational sites with faulty apps, many banks and credit card apps are glitchy too. A common issue is lack of detail / delayed updating. Also, version and hardware differences which can cause apps to act wonky. I use a well known, large on-line bank, and their website updates account balances nearly immediately while their app often doesn't.
As for the couple, they'll likely come up empty. What works against their argument is the lack of funds they had when first attempting to purchase the ticket. Regardless, lotteries and other gambling establishments near never pay out when there's even a question of a ticket / machine being faulty.