Nikon D50 err code

Hello. I have a Nikon D50 28-100 kit lens. I put another Nikon DX lenses again yesterday for the first time when I insert my own lens "ERR" gave the error. Curtain opening and closing the shutter button is pressed quickly a few times and again "ERR" gives the error. I tried everything but the error continues. What is the problem how to fix me, I would be happy if you can help. thx