If the SIM is not in the tray 1 (in a pocket under one little cover on the right side of the tray), you need to contact your local Xerox support centre.
First you must check the SBC fan(the board with network port on it, it have two thumb screws) if is working well. And if the fan is in good condition you need to reinstall the machine firmware by AltBoot-ing.
I was having a problem with this machine Xerox 7225 for a week now.
Screen is showing Device is not available but after a minute or so it will work then it will go back again. then error again "no services to display" then it will print again. then device is not available again causing a lot of delay on printing and copying. cycle keeps going on.
any help will be much appriciated.