Cannot view PDF - authorization required

I am trying to dyncamically generate PDFs from an HTML view in my application using the following code:

$url = base_url() . "profile/" . $payment->user_id . "/voucher/" . $payment->reward_id;

        try {   
            // create an API client instance
            $client = new Pdfcrowd($name, $api_key);
            // convert a web page and store the generated PDF into a $pdf variable
            $pdf = $client->convertURI($url);

            // set HTTP response headers
            header("Content-Type: application/pdf");
            header("Cache-Control: no-cache");
            header("Accept-Ranges: none");
            header("Content-Disposition: inline; filename=\"voucher.pdf\"");

            echo $pdf;
        }

         catch (PdfcrowdException $why) {
            echo "Can't create PDF: ".$why."\n";
        }

When the pages load, the header is set to application/pdf, but I just see a blank white page with the following error:

Authorization Required
This server could not verify that you are authorized to access the document requested. Either you supplied
the wrong credentials (e.g., bad password), or your browser doesn't understand how to supply the
credentials required.

Is this some sort of htaccess issue? I am stumped. Please help!

It seems the page is password protected. What is the page URL?

The URL is getting generated dynamically based off a user ID number and purchase order. I can access the same page as an admin when I create only a HTML file and don't try to convert it to PDF.

You are saying that you can access the page as an admin which indicates that the page is password protected and is not accessible publicly.

If your application uses basic authentication (i.e. using .htaccess) you can specify user/password like this: http://user:password@server.com/app

The API does not support cookie/session based authentication at this moment so if your application uses this type of authentication then it is not possible to convert such page.

Yes, I'm trying to use this to generate specific vouchers that users could use to claim their purchases. It would only be accessible from logged in users using session based authentication. Bummed to hear this won't work with your API, but thanks for the support.

Not sure if this is an option for your but a possible workaround is to make the user specific voucher temporarily accessible (ideally just for the API call) on a public but impossible-to-guess URL.