What is the make and model of your printer?
The tiniest piece of paper on a sensor will make the printer think it still has a jam...
Go through the instructions in the manual again, look with a flashlight into all the paper feed points and follow the steps, remove cartridges and paper trays and check carefully, you may need tweezers to get to the any torn bits of paper or dust.
Try a power down reset, unplug from the wall wait 10 seconds and repower..
If no luck it may be that you have a faulty paper sensor...
Is the printer still under warranty?