None of the replies I read seem to have any effect on what I am seeing, or seem irrelevant. OF COURSE the contents of Tray 1 (MPT) are unspecified, because it is SUPPOSED TO BE EMPTY. I read one reply which told me that I should use the "Administrative" tab to set Tray 1 to "Dynamic". I have no idea what antique version of the software this is referring to, but I cannot find an administrative tab, or anything resembling it, even when logged into my administrative account; I can find nothing about setting trays to static or dynamic. I have the latest drivers. Nothing seems to help. No matter what I do, it keeps telling me that Tray 1 is empty. After spending some time on this problem this afternoon, I have made it worse, because even if I explicitly select-by-tray Tray 2 (Letter), it now insists on using Tray 1. What is going on here? How can I get this printer to start working again? (A few weeks ago, another user printed some labels from the MPT. Now it won't acknowledge that any other tray exists). And yes, I have configured it for all the extra trays, and the hard drive. It knows the trays exist; it even knows what paper is in them (letter, legal, or tabloid). But it won't use them.
If you are printing from MS Office, you would need to change whatever the other user did in Page Setup