when you say you have tried everything.. Have you tried these steps.
1. Remove all the ink cartridges, now, with the machine open turn the machine off, turn it back on and watch the ink carriage/printhead. When it makes its sweep left to right when the printer starts, unplug the machine when the printhead has moved out of its "parked " position. This will let you see under where the printhead normally sits. Now, use a bright light and inspect under where the ink cartridges were and under where the printhead was. Do you see any paper, debris, or any parts showing out of place?
2. With the cartridges removed, turn the machine upside down and shake it, do you hear or see anything fall loose?
3. Fold two pieces of paper in half longways, and try to push them slowly through the machine in the normal direction that paper travels, this may knock any hidden debris or paper loose inside the machine.
4. Now, as far as the scanner cover open message.. Let me explain how the machine can sense the scanner cover is open. Either on one of the hinges, or on the latch or protruding plastic pieces where the scanner cover closes there will be a sensor. That sensor could be stuck, or it could have paper or debris not allowing the sensor to close.
Thoroughly inspect each hinge, and any place you see where any plastic pegs would protrude from the top cover into the bottom cover. Inspect every point under the scanner cover to see if you can find where the sensor is. Now, these sensors are sometimes spring loaded pieces of plastic, or plastic "wheels" or gears that are supposed to depress or recede when something hits them. so when it says scanner cover open, there is a sensor that is either not being pressed, or its stuck so that the machine thinks the scanner cover is open even when its not.
If all else fails, reading slowly and thoroughly through this long page will give you a lot of ideas and will help educate you as to how jams and covers are sensed by the machine, with a lot of varied repair steps thrown in.
If you have any questions at all, I look forward to hearing from you later today. This is definitely an issue that I would like to see resolved, as so many good machines are tossed into the trash over a simple lever or sensor being stuck ( and almost all sensors on that machine are mechanical meaning they can be unstuck once you find them )
Senior Technician and Network Switching Systems Operator / Maintainer.