Is the beep after one minute? If so, my guess is that you don't have the cable release socket on the lens screwed all the way in, i.e. some red ring is probably showing. That means the lens is waiting for a cable release to trip it, and the body beeps after a minute if you don't trip the lens.
Put a cable release on the lens, screw it in real tight, and then remove it - you should see the silver ring that it screws into retract fully into the lens.
PS the above assumes the mirror goes up when you trip the body. If not, then it's a different problem. Maybe bad contacts on the lens mount. Do you have another lens to test with?