A QR code doesn't work - why could this happen?

I got the QR code coupon for a discount (and a very fine one, as described in the email) in the local store. Tried to scan it - it doesn't work. Tried with my wife's phone - nothing. I do scan QR codes now and then, but never created one. What I'm trying to say is - I have no idea why a QR code wouldn't work. Of course, I am planning either to drop by or to send them an email, getting the discount won't be an issue, but I would really like to help these people. It's a very nice family and I know they're struggling a bit lately (I mean, who doesn't). So I seriously doubt they invested a lot in marketing or hired someone to do this campaign for them. I want to tell them possible reasons for this and perhaps recommend a QR code generator (there are some free ones, that much I know). Can anyone help me out here?

True, to be able to tell you more, we should see it. But I'll mention some possible options anyway. If a QR code leads to a broken link (like a dead website or URL error), it won't work. If you use a lousy QR code generator, you might end up with codes that expire or don't work well. To avoid this, look for a QR code generator with good reviews. I did my own "best qr code generator" search last year, found a reliable and free one I've been using since then (Beaconstac), but most of these will do.

Putting too much stuff into a QR code can slow down scanning and lead to problems. The general recommendation is to keep it simple and clean for faster and reliable scanning. Also, a QR code should be at least 2x2 cm and not too small or too large, depending on where you're using it. Changing the colors of your QR code can be fun, but if they blend in with the background, it won't scan. It's important that the code's foreground (the black part) is noticeably darker than the background for clear scanning. Dull colors won't help either. Sometimes, blurry QR codes are the problem. This happens when you resize them incorrectly. To fix this, one should download a QR code in a high-resolution format, like SVG or PNG, to keep it sharp and clear.

Okay, I got too chatty, sorry. I'll just add it's nice that you want to help these people, it's sort of rare these days. Cheers!

Thank you, guys, I ended up learning a lot about these little things. Will take some notes and forward them to the store owners. I am sure I can thank you on their behalf too. No community like this one!