Canon iR 2520 paper jam on double sided .

[Mukasa]

Hello Friends ,
I have a Desktop Canon iR 2520 which failed feeding papers in the tray 1 using landscape i only feed it portrait , but now it has even failed two sided coping and printing
it jams in the two sided section.
Help me out so that i can feed paper using both Landscape and portrait also copying or printing double sided .

Thanks
Muks