There is a known issue which may be the cause of your "access is denied" message. Are you using Safari as your browser?
If so then your issue is related to the handling of third party cookies in Safari. You have 3 options:
You can use a different browser - Firefox, Chrome or Microsoft Edge.
Follow the steps to allow third party cookies for Safari (see below)
Try to refresh the Safari browser by clearing the Cookies and Clear Cache.
How to allow Session Cookies in Safari browser:
The modal/window will pop up when a merchant is using Safari as their browser and the browser is not yet configured to allow it.
Please open your Turn 14 app while in your Safari browser.Then follow these steps: https://www.whatismybrowser.com/guides/how-to-enable-cookies/safari