This may be completely irrelevant since you don't say what kind of error you are getting or how you are trying to feed the paper.
If, as you suggest in the last post, you are using the rear slot then this requires both practice and patience. When I first got a 3800 (essentially the same printer) it took me at least 7 or 8 goes to get a sheet to feed through the rear slot. I consistently got paper skew errors. The printer checks to see if the paper is perfectly straight and if not will reject it. You can in fact by-pass this by turning off the "check paper size" option in the menu on the lcd and it will load paper however badly skewed. However the trick, not really a trick, is to take enormous care when feeding. What works for me is to make sure that the left hand edge of the paper (right hand side as you look at it if loading it whilst standing in front of the printer) is absolutely flush with the edge of the fixed paper guide. Then feed the paper in by exerting equal pressure on both sides of the paper. It helps to open the front top panel so that you watch how the paper is taken into the printer. If you exert unequal pressure on the paper when feeding then it doesn't go in perfectly straight and you will get a paper skew error.
The only way is to keep on doing it until you get it right. Now I virtually never (famous last words) get an error loading A2 paper from the rear feed but it was a source of enormous frustration when I first tried it and I was convinced that there was something wrong with the printer.