This error can occur when PDF requests are routed to a server where the required PDF service is unavailable. In the reported case, the customer was using an older Apsona package version where the AC83ServerRegion FMA parameter also controlled the PDF server URL. The parameter had been set to 18, causing PDF requests to be routed to Node 18, which did not have an available PDF server.
Engineering reverted the AC83ServerRegion parameter to 0, after which PDF requests were correctly routed to Node 05 and Node 06, and PDF generation resumed successfully. The customer was also advised to upgrade to the latest Apsona package, which includes a fix preventing the server-region FMA from incorrectly updating the PDF server URL.