Full stop, clean jam.

I have a problem with my HP Officejet 7310 all-in-one. there is a "full stop. open door and clear jam". there has been a jam, but there is no more. Printer cartridges left out in the left side and can not really get to hear the page. On the right side where the strap sits, I fjerneet no "paper" which may well have been a cog in the strap. Now there is only one pole as the belt runs. it may be the problem or you have other suggestions?