If you are feeling brave (I say this because if it is dead, it could be stinky and rotten) you could try making a safety hole in the black area, in case the baby has bruised the shell there from trying to pip. It’s possible you aren’t seeing the aircell because the baby has now pushed into the aircell and is filling it. But it’s also possible it’s dead
Well if it is alive and you make a tiny safety hole ( use a screw or drill bit, make it pin hole sized), you may start hearing clicking or peeping if it is alive.
If after doing that and you see or hear nothing after a few hours I might carefully chip the hole a little bit bigger, moisten the membrane, check for veins. You might discover at this point that it is dead or rotten
If you’re hearing nothing and seeing no movement - that’s definitely not good.
Day 30 was the last time you saw movement? If so it could be long dead