Oki b6300 has problem picking up sheets and therefore I get a jam message when actual it is not jammed , but the paper wasn't picked up.

Pull out the tray and check the rubber roller assembly attached to the black removable piece of the tray. Check to be sure the rubber rollers have no flat spots, if they do, replace them. This black piece comes off and underneath should be a small spring. This spring sometimes comes off and the rollers do not remain upright. We have over 50 B6300s in service at my location and this is the most common "paper feed" issue we run into with these printers. Pull out the tray and check the rubber roller assembly attached to the black removable piece of the tray. Check to be sure the rubber rollers have no flat spots, if they do, replace them. This black piece comes off and underneath should be a small spring. This spring sometimes comes off and the rollers do not remain upright. We have over 50 B6300s in service at my location and this is the most common "paper feed" issue we run into with these printers.