We’ve built a java web service that we deploy for a few different Zoom customers (integrates Pardot with Zoom Webinars).
Many customers have reported that at 9am ET every Saturday morning, they (and I for my own deployment) get a Zoom Marketplace email saying that our webhook is not responsive and failed to respond to the validation request. Looking at our logs, everything replied just fine.
I’m pretty sure it’s not my web service, as for one of my Server-to-Server apps it’s actually some Server side JS code that is returning the verification code. Manually clicking the verify code button clears the Zoom error state.