OfficeJet Pro 7740 thinks tray 1 is empty but it isn't - it has 11x17. won't print

[david47408]

I previously had printed onto tabloid with no problem.

Now the printer won't print.  Says:

Load Plain Paper

(Tabloid 11x17)

paper in tray 1

confirm guides are in

[david47408]

PS:

I put 11x17 in tray 2 and was able to print.

I put letter size in tray 1 and the printer still thinks the tray is empty.