Check the spaces around the print head carriage to assure that nothing is
blocking its movement. Check the paper path for obstacles such as bits of
paper or the pet gerbil you have not been able to find. Locate the carriage
motor and assure that nothing is impeding the rotation of the shaft and
attached gears. Check the drive belt or string and assure it is not broken
or detached.
Failing any home-repairable problem, I think the printer will need servicing
or replacing.
