I have a c4150. it will not print, but will print a copy. error msg :free carriage cradle comes up

I have a c 4150 that will not print from the computer, it will print from "copy" mode.  Error messages is: free carriage cradle"  The carriage moves freely, there is no paper jam front or back, the self-test prints fine.  I have unplugged it, removed and replaced cartridges.  What else can I do????