We have a Workcentre 7220 that is becoming a major thorn in my side.
The printer has 5 trays installed (including the bypass) and it sees them all in the device configuration and the web interface; but only the first 2 trays are shown in the driver / printer properties; and as a result, users can't print to paper in those trays either manually or via automatic selection.
You have to select how many trays that's installed in ur driver settings.
Go to Start -> Devices and Printers -> Right click and choose Printer Preferences -> Configuration and under installable options you can choose how many "Paper trays" that are installed.
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The 7220 has no configurations where there are only 2 trays, which means the driver you are using is not for this printer.
If it is on a Mac I can only assume you are printing with Apples "Generic PS"
If it is a PC it is either a driver that was installed for an older printer and this one was dropped into the same IP address, or a Global Xerox driver set to "Basic Print Mode" instead of the machine model, which happens when using a Global driver older than the product or when the port is wrong and or the SNMP is disabled.