Used nikon d90 won't turn on?

This is probably a very silly question, but I recently bought a nikon d90 used off amazon and got it in the mail yesterday. I charged the battery, put on a lens, put in a memory card, but when I turn it on the only thing that happens is the top screen shows aperture, shutter speed, etc - the lcd does not show anything, and the camera does not respond when you try to take a photo.
Is there something that I'm missing - something really stupid that enables you to turn a camera on? Or did I stupidly buy a broken camera?

Does the Control Panel (the top screen) show that the battery is fully charged?
The monitor (the rear LCD) should turn on briefly and then go off. The Info, Menu, or Playback button should bring the monitor back on.
If you shoot in Auto you should get a picture. If the scene lacks a good enough edge for the autofocus to lock onto it can stall. Switching to manual focus should get you a picture, even if it is not a well focused one. Miscommunications with the lens or SD card may show up as E or EE.

Withe the camera off push the switch all the way to the other side and release. The rear display should show the same information on it as the top lcd.

Read How to reset a D-SLR to factory default settings
https://nikoneurope-en.custhelp.com/app/answers/detail/a_id/9933/~/how-to-reset-a-d-slr-to-factory-default-settings

Also you know that the rear display is not like a Point and shoo camera. You look thru the view finder to compose a shot. The rear display should become active if you press the LV (live View) button. In LV you consume battery power and overheat the camera if used for prolong periods of time.

Update us on your progress of this matter, also what lens are you using?