While setting up a new Postscript printer to be used with the Automation Engine Print ticket, the error "Unknown PPD specified in ticket" appears when you open the print ticket and select the new printer.
Opening the Print ticket in Automation Engine Pilot gives an "Unknown PPD specified in ticket" error.
After installation of the postscript printer, you need to restart the Automation Engine processes that use the PPDs: in Windows Task Manager, stop ppdsrv.exe(*32) and printsrv.exe(*32). They will automatically start again when the print ticket is addressed. Restart the Automation Engine Pilot as well.
If that does not help, you should restart the Automation Engine Server software. This can be done on the Automation Engine Server Admin web page > Status Overview category then stop and start server.