There could be many things that would cause this(paper tray needs to be replaced, paper is stuck behind the tray, guides aren't tight against edges of paper, etc.)
It's really hard to diagnose without eliminating some of these possible causes first.
You might want to try doing a search in the knowledge base to try to narrow it down to your specific issue:
display of the printer and will not let anything print
Okay. So do the error messages come through the print driver, or on the display of the printer?
How do the users connect to these printers? Ethernet, USB or wireless?
We have numerous of these printers in our office and at various times they will claim that the paper is out when in fact it is full. Or it will claim that a tray is missing when it is not. This is very bothersome for our business needs and is a real headache. What causes this or what steps can be taken to clear this so it does not hender production?