It's because you forgot the apostrophe. I'm just kidding idk

The Wii U seems to not like "give up", but I don't know why. In SMM2, you can't type "like this" or "いいね" (the "I like it!" button in Japanese), presumably to prevent begging for likes. Maybe there's something similar here, i.e. to prevent saying "You'll never win! Give up!"?

At any rate, if you need to get around the word filter, try substituting characters. Here, you can replace the English letter "e" with the Cyrillic character "е" on page 9 of Symbols. (Of course, please don't abuse this technique.)