PIXMA PRO-100 won't load paper

[BarryInSeattle]

I haven't used my PRO-100 for a couple of years, but decide to dust it off to print some photos.

Unfortunately, I'm stymied by the fac that the printer refuses to load paper, either via the manual feed or the rear try.  

Rear tray:  I hear lots of moving parts, but the paper never seems to start feeding. I've tried  a few pages, and 15 pages, and double-checked the alignment numerous times, but no luck. After ~30 seconds of loading noises, the error light comes on showing 2 flashes, indicative of paper out.

Manual feed tray:  There's more activity here, the paper is pulled down into the feed... but then it stops and, again, the dreaded error light flashes.  With the paper already partially fed, I've tried pushing the button to Resume, but then the error light switches to 3 flashes indicating a paper jam.

So as it is, I have no way to load paper, and thus no way to print.  😕  
Anyone have other ideas?

[BarryInSeattle]

Hi, and thanks for  your suggestions!

The printer was clean (I keep it covered), but I did try powering off & unplugging without any change.  However, on a lark I decided to try a piece of large-format (& costly) paper.  After much whirring and clicking, the manual feed pulled in the paper and printed nicely.  🙂  Then I went back to trying letter-size... and it worked!
All I can imagine is that there was an issue with the rollers near the center of the feed - maybe they were stuck, or slipping? - and that after the large paper was pulled through it somehow got them to work.  Seems a bit like jiggling the handle of a recalcitrant toilet.... but in any case, I'm back in business.