HP LaserJet Enterprise M607 --- do not understand paper trays -

[onb4unoit]

Ever since I got this printer, it's been hard to control the paper settings.

I want the printer to automatically default to the lower paper tray (Tray 2 - which holds 550 sheets of paper.) EXCEPT when I have placed paper or envelope in the multipurpose tray (Tray 1).

I had the printer doing pretty well, but suddenly I'm getting the following message in the display box:

Load Tray 2 - Plain, Letter

To use another tray, select options....

When I select options, it displays:

Use Another Tray

Tray 2, Any type, any Custom   OK or cancel.

I'm having to do this for each sheet of paper that I print - I cannot figure out how to reset it or change it!

HELP!

Thank you .... [Personal Information Removed]

[Repairatrooper]

One of two things will cause tray 2 to not detect paper properly. Either the guides are out of place or you have manually over-ridden the paper size settings.  Remove the tray, ensure that all guides are set for letter and observe behaviour when you reinsert the tray. If the tray does not read letter then it is possible that the size guide on the side of the tray has come loose or the switch inside is bad. We have had cases where the size guides have come loose. Remove tray and turn it over and make sure that the guide (circled red in picture) look the same as this. If the metal tab is not over the nylon part then tray size selection will not work properly. You will have to work the two pieces back into their proper place.