PSPDFKit Server has been deprecated and replaced by PSPDFKit Document Engine. All PSPDFKit Server and PSPDFKit for Web Server-Backed licenses will work as before and be supported until 15 May 2024 (we will contact you about license migration). To start using Document Engine, refer to the migration guide. With Document Engine, you’ll have access to robust new capabilities (read the blog for more information).
The 504 response may be sent by your proxy server. Make sure to increase the timeouts of your proxy server to ensure that responses from PSPDFKit Server get redirected to the clients.