PDF.js Express Viewer not working via reverse proxies

Which product are you using?
PDF.js Express Viewer

PDF.js Express Version
@pdftron/pdfjs-express-viewer: 8.1.1

Detailed description of issue
We have replaced react-pdfwith pdfjs-express-viewer on our website https://edu.digitaltheatreplus.com. It is working for most of our customers, except for those that use our website via a reverse proxy (which has a different domain name) for example: https://edu-digitaltheatreplus-com.eu1.proxy.openathens.net

We have examined HAR files from customers, and see that the request to GET /auth.pdfjs.express/
returns a 200 and a key, however, users do not see the PDF, they see the following:

Screenshot 2021-12-09 at 23.11.55

My assumption is that the problem is that the key doesn’t validate the domain/referrer, is that correct? Is there a way to generate a key that allows for the same website to work via reverse proxy/different domains?

Any ideas of advice would be gratefully received, this was implemented by a developer in haste before they left our business, so I’m left with the decision of finding a way to make PDF.js Express Viewer work via reverse proxy, or roll back to our old react-pdf implementation.

Expected behaviour
PDF document is displayed

Does your issue happen with every document, or just one?
Every document when loaded by a reverse proxy (we have about 1500 customers using either OpenAthens, WAM Proxy or EZProxy)

Link to document
Unfortunately they are behind a paywall, also, you’d need to be using a reverse proxy to reproduce issue.

Code snippet

const PdfViewer = dynamic(
  () => import('../../../media/components/pdf-viewer'),
  { ssr: false }
);
...
        <PdfViewer
            key={[
              guide.media.url,
              printAndDownloadDisabled,
              outlineHidden,
            ].join()}
            pdfUrl={guide.media.url}
            pdfTitle={guide.name}
            disablePrintAndDownload={printAndDownloadDisabled !== 'off'}
            hideOutline={outlineHidden}
          />

Hello, I’m Ron, an automated tech support bot :robot:

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Hey there!

All requests made to our authentication server must come from the domain/host that is specified on the license key. In your case when using a reverse proxy, the requests no longer come from your configured host which is why the viewer will not load.

I’ll DM you with some things we can do.

Logan