If you have a Zoom webinar scheduled and it's stuck on "Please wait for the host to start this webinar", you should check if you or someone on your team has accidentally logged in as the main host.
Zoom will send the API a 'webinar started' message, which stops our automation from starting it up (system thinks because of this it was successfully started).
Best Practise is to have your webinars hosted on a separate dedicated Zoom account, which you can "lose the password" to and therefore no-one will accidentally log in as the main host.