Print Head assembley won't move to the center

I have a Canon PIXMA iP7260 printer. I need to replace a cartridge bu the print head assembly will not move to the center. The service code is 6000. I have followed the advice in a similar thread but without success. I cannot physically move the print head. I have tried pushing the cartridges down in case they are not seated properly but without any luck. Is it possible that the printer has reached the en of its life? It would be cheaper for me to buy a new printer than get to have this one repaired, but I live in hope that someone will have a fix.