Webhook URL not accessible - getting Error 404

Why do I keep getting error 404 message?

Using Velo - Backend

Hi everyone,
I am working with a developer to use webhooks so that Stripe can send payment succeeded information to my wix site.
We want Stripe to tell Wix that a user has paid, so that wix automaticallt assigns them as a “Paid Member” role, to ensure that they can access our paid membership area.
Please note: I am sending customers to pay through specific Stripe Payment links for VAT reasons, the wix checkout for pricing plans is too limited in terms of VAT for me to simply use Stripe as the payment processor via wix.

What have you already tried:
My developer has tried to simplify the code as much as possible. For some reason although it is published, the URL for the webhook is not accessible. It seems like it is being blocked.

FYI - I have the Business Plan, could this be part of the issue? Is it necessary to have the Business Elite plan for this?
Also out current file format is .js

Any ideas?