When trying to run the setup script to upgrade Kayako Classic on the IIS server, you might see the '403 Forbidden: Access is denied' error.
The 403 Forbidden error is an HTTP status code that means that accessing the page or directory you were trying to reach is absolutely forbidden for some reason.
To resolve this issue, you need to enable directory browsing for your Kayako Classic application. To enable directory browsing on IIS, check out the steps from this Microsoft document.
Another thing to consider when dealing with this issue is to check for URL errors and make sure you're specifying an actual web page file name and extension, not just a directory. Most websites are configured to disallow directory browsing, so a 403 Forbidden message may appear when trying to display a folder instead of a specific page.
For example, check if the setup URL is using the following format:
This format is telling the server that the request is to browse the website's directory because of the forward-slash "/" at the end of the URL. Hence making sure there is no forward slash "/" at the end of the URL string should solve the problem.
The setup URL should be (without the forward-slash "/") :