Your best bet with power off is to remove the covers in order to directly work on the area. Any slight of hand, twiddling from the side with covers on may work, but frustration comes quickly. More important, you may break or find a broken part. More than likely the ink cart got unseated then jammed. Also, if left for a longtime, any excessive ink may have dried the parking cup/seal and got stuck. -OR- the belt broke, etc. a direct view is best to see what has to be done. HP parts surfer offers a detailed view of items to see what you're dealing with, use that as a guide, though it does tell you how to remove covers, use common sense.
My HP 5650 Printer has the ink cartridges jammed at the right side. The platform that supports the ink cartridges is stuck in the up position which prevents the cartridges from being removed or printing. Does anyone have an idea on how to fix this? The printer is less than a year old.