You can navigate to it from the print driver. Select "Printing Preferences", navigate to the Advanced tab, expand "Xerox Web Links", select it and then "Open". Then select "System Status". From there you should be able to see any alerts and corresponding error codes.
I uploaded a screen capture of the print driver where the System Status link is.
Try turning the printer off and back on (assuming you haven't already). Also, if it will print, try printing normally and see if the machine refreshes itself.
If the message won't go away or won't print, navigate to the CentreWare Internet Services home page (open the IP address of the printer in an Internet Browser) and share what the alert status is here. If there is an error code displayed it might help diagnose the issue.
About one week ago my Phaser 7100 printer said I needed to replace the waste toner cartridge, with I did.
Today I get the message on my printer "replace the waste toner cartridge", surely I don't need to replace it again, after only a week?