The fastest way to narrow this down is to split it into two questions: does any request reach Make at all, and is your form actually sending one.
Start at the webhook module. Open the scenario, click the webhook, and look at the queue. Submit the form once, then check the queue again. If it stays at zero, no request ever arrived and nothing downstream matters yet.
One thing to set aside first: the fact that the URL loads normally in a browser only proves the webhook exists. Opening it is a GET with no body, and a working hook answers that with Accepted no matter what your form does.
If nothing arrives, check these in order.
First, what the form actually does on submit. A plain HTML form whose action is the webhook URL sends a normal POST and that works. A page builder form (Webflow, Wix, Elementor, most WordPress form plugins) posts to its own endpoint instead, and a webhook field in its settings is often only honoured if that builder has a real webhook integration. Confirm it in the browser: open the developer tools, go to the Network tab, submit the form, and look for a request going to the Make hook domain. If there is no such request, the form never calls Make and the problem is entirely on the website side.
Second, if you do see the request, read its status. If you submit by fetch or ajax with a custom content type, the browser sends a preflight first, and a failed preflight blocks the real request before Make ever sees it. Sending the body as form data or as text/plain avoids that preflight.
Third, if the request goes out and comes back with 200 but the scenario does nothing, check that the scenario is switched on, and that this webhook is not also attached to another scenario. A webhook belongs to exactly one scenario, so if the URL was reused, the data is landing in the other one.
If the queue does count up and the scenario still fails, it is usually the data structure. Click Redetermine data structure on the webhook, submit the form once while it is waiting, and the fields become available for mapping.
Knowing which half fails, request never sent or request sent but not processed, will point straight at the fix.