What's your most embarrassing sales mistake?

I've just started doing cold emails, and today I got this enthusiastic reply... with a small caveat:

Thank you for building this!! I really mean it.

I did try to use it, except it crashes and doesn't work.

🤦‍♂️ D'oh!

I know it's not huge, but I'm definitely embarrassed!

Please, help me feel better; what are your embarrassing sales mistakes!?