Hi, I have this printer and I too had this problem, there seemed to be no paper stuck in there.
I removed the two screws at the top rear and two screws at the top front behind the cartridge flap, this enables the whole of the top of the printer to be hinged up and back.
On the right hand side there is a device which I think cleans the print head, it's covered in ink so you're going to get dirty hands.
There was paper jammed in the gear mechanism on mine which couldn't be seen before. I removed all the paper but I still got the jammed message.
I noticed that the gear mechanism on the head cleaner device was sticking, the white gear should disengage from the printer mechanism when the printer head moves away from the cleaning device. On mine it was staying engaged and jamming the printer,it was gummed up with ink.
I cleaned the gear and mechanism with some brake and clutch cleaning solvent I had in the garage and lubricated with WD40. I worked the mechanism by hand for a while until it was free.
I reassembled and hey presto! Working Printer!