I'm guessing this has something to do with the sensors but my 7800 will error on paper that has been printed on when I put it back in for the gloss.
So I troubleshooted.
I can load new cut sheet fine 10 out of 10 times.
Once printed on it will give me the load paper properly error message after attempting to load it. Just to be sure it wasn't an edge issue I turned it around and it loaded just fine. Turned it back around and the printer attempted and then gave me the load paper properly error message. (I've done this numerous times) Sometimes I can get around it by putting the paper in landscape but it's erring on that now as well.
Spec Ed has gloss in the first run through so I removed the gloss in the profile to see if that was the issue and it didn't change the situation.
I'm printing on Ilford Gold Fibre 13x19. the image size is 12x18. I have not tried making the image smaller to see if that makes a difference and that is the logical next step but thought I'd run this by you first to see if this is something you've had experience with.