The other day I tried to buy a $25 gift card for my brother's birthday. The coffee shop had plenty of cards in stock but they couldn't add value to the card because the machine was broken. After trying for 10 minutes, they ended up giving me the card for free.
Sometimes you don't know you have a problem until someone else asks. The request is typically new but it can just as easily be about something old that should already be working.
Anticipating the use of fundamentals is a key to success. If you don't use your basic skills, you're bound to drop the ball such as what happened at the coffee shop.
Sometimes the things that break are the most obvious. Check or practice often enough to ensure everything is still working. Nothing just works by default.