As you've taken out the toner and shaken it, The only other thing I would before contacting support is power off and then power on the device.
If that does not work, I recommend contacting your local Xerox Support Department to speak with a Product Specialist for more assistance.
Xerox B235 wont print unless we change to NEW Toner cartridge. We changed and code still says same thing.
took toner out and tapped and shook to re distribute toner material. replaced the cartridge into the printer
and still saying Replace imaging unit.