I remember trying to order from a pizza place that talked to a third party delivery site, I hit "Order" and the browser didn't do anything. DevTools told me it tried to talk to the 3rd party using HTTP although the page was in HTTPS, and the browser blocked it (this was years ago when browsers started blocking HTTP content on HTTPS sites). Modifying the submit URL to https solved the problem.

I found it pretty funny that I had to understand web development and troubleshoot the problem just to order pizza...