My Canon MG 3620 printer had been giving me a 1003 error code when paper was correctly loaded. I followed the advice found elsewhere on this forum (unplug and power down 3x), which at least got the paper to *start* loading. But unfortunately, it just pulled the paper halfway in and stopped, resulting in a "paper jam" message.
I can find instructions for clearing the jam from inside or from the output tray, but my paper hasn't gotten that far in (I don't see anything when I open from the front or the back). The only reference I can find to clearing a jam from the input tray is a warning not to pull it out toward me, which is the only way I can see that I could get it out (seems like it would pull out fairly easily). I may need to clean the print rollers, but the first step is to take out any paper, so I can't try till I get the paper out.