401 implies you’re passing an invalid application id. Based on the link provided, you should be using your production application id; in your previous post you mentioned sandbox, so I imagine you’re loading the production payment form (squareup.com... instead of squareupsandbox.com...) and passing the sandbox application id which is causing this 401 error.
So this website link https://handsfreeluggage dot com/appointment-booking/ is a production payment form and sandbox application ID should not be used in the backend on the WordPress website? Am I right?
So if I want to use the sandbox payment form, how does that look like.
Lastly, when In production mode, does the test data link you provided earlier works for production or does the test data only work for sandbox?
Since you’re using a third party solution, they really should handle the switching between sandbox and production for you. If they have a sandbox mode, you should supply your sandbox application id, whereas the production mode you should supply your production application id (which can be found in your developer dashboard on Square’s side).
As for testing, those values will only work while in sandbox. In production, they would return a card declined error.