Printing from an AS400 causes a prompt on the printer display to select an available tray. This is a known problem on the following models HP LJ 4250, HP LJ 9050, and HP M3035 printers. This is caused by the limited driver selection on AS400. Printing directed through this server directs print to Tray 1. Since Tray 1 is not loaded, the printer prompts for user intervention to redirect print to loaded tray. To fix this, you can modify printer settings to automatically try another tray, preventing prompt and user intervention during print. [more]
Steps for modification:
From web interface, select settings Tab
Browse to the following Menu: Configure Device>System Setup> Tray Behavior
Set Use Requested Tray to First (default is Exclusively). This will allow print coming to tray one to be redirected to the next available tray without user interaction.
NOTE: The actual menu options may be different for different models. The menu names above were taken from the 9050 model.