How to get Stylus DX4850 to feed paper to the print point?

The paper won't feed for actual printing. You can get it to feed right through the printer but when it needs to lay ink on paper the error light comes on against paper. To be sure it is paper I've checked the ink cartridges in the approved manner and the machine finds no fault with any of them. I've also tried to make a copy from the scanner but once the scan head has completed its run the error light comes on again.
What can I do to get the paper to feed into the print position?