| Solution found Thanks for your help!!!
Here is what really helped.
Works with ERROR C6000, C6300, C6400
Switch off
Open Toner Cover
Switch on, holding "System Menu"
Go to "Secure Setting"
"Enter"
Hold "Start" "#" "Enter"
Scoll down to "Maintenance Mode"
"Enter"
Scoll down to "U163"
Scoll do "Execute"
"Enter"
Close Toner Cover
Leave run for a few seconds
Switch off
Switch on |