Why it's no display and when I view in viewfinder it says "LENS"

@marksdee the "Lens" display means that the camera body cannot establish communication with the attached lens. As a safety protocol, the camera locks the shutter because it cannot read or control the aperture blades. Start by cleaning the contacts between the camera and the body.

• Remove the lens from the camera body.
• IMPORTANT! Turn the camera body so the opening faces downward (to prevent debris from falling onto the reflex mirror or sensor).
• Use a clean pencil eraser (the pink or white rubber type) or a microfiber cloth dipped in +90% isopropyl alcohol.
• Gently scrub the curved row of small gold contact pins inside the camera mount flange, and repeat the process on the corresponding flat metal pads on the back of the lens.
• Blow away any eraser crumbs with a hand blower, remount the lens firmly until it clicks, and turn the camera back on.

There may also be issues with the Lens Release Pin Alignment. Look at the lens release button on the front of the camera body. Grip the lens while it is mounted and try to twist it slightly without pressing the release button. If there is excessive wiggle or play, the metal lens mount flange may be loose. Tighten the small Phillips-head screws on the camera mount and the lens backing plate if you find any wobble.

You can download the SM for your camera at the Documents header on this page Sony Alpha DSLR-A500