Can't print from Tray 1 like I use to

[LadyDi41]

My HP Laserjet printer P3015 prints everything from Tray 2 which contains plain letter paper all the time.  If I want to print a letterhead, I put a sheet in Tray 1.  It use to print from Tray 1, but no longer does so.  It prints from Tray 2.  I end up having to put the letterhead in Tray 2 to get it to print.  I want it to print from Tray 1 when I've loaded it with letterhead.  Please help.  My trays are configured to letter size and any type in both trays. Don't know what to do.  Step by step instruction please.   

[dansdaduk]

>> ... My trays are configured to letter size and any type in both trays ...

That's part of the problem; with those settings, the printer has no way of distinguishing the trays, other than via their tray identifiers.

With a print request, the required paper (media) source is determined by a mix of three attributes:

• Paper size (e.g. A4 or Letter).
• Paper type (e.g. Plain or Letterhead).
• Paper source (e.g. Auto-select or printer-specific tray identifer).

The printer will attempt to match whatever is in the print request (in terms of these attributes) with what it believes it has in each of its trays.