Ugh, QR codes can be such a pain sometimes! I was trying to scan one the other day for a discount at my favorite café, and it just wouldn't work no matter how I angled my phone. The lighting was fine, my camera was clean, but nada. Turns out, the code was printed super tiny on a crumpled receipt, and the contrast was awful—barely any difference between the black and white parts. I ended up squinting at it like some kind of detective, haha. If the code's too small or blurry, most scanners just give up. Also, if there's glare or reflections, forget it. My pro tip? Try zooming in or stepping back slightly to adjust the focus. Sometimes it's just about finding that sweet spot where your phone finally goes 'aha!' and recognizes it.
Another thing I learned the hard way: not all QR codes are created equal. Some are just badly designed, with weird shapes or missing alignment markers. And if the code is damaged—like scratched or folded—good luck. I once spent ten minutes trying to scan a flyer that had been left in the rain. Spoiler: it didn't end well. If you're generating your own codes, test them on multiple devices before printing. And if you're scanning, patience (and maybe better lighting) is key.