DHCP does not belong to your antminer -- it belongs to your router, when you set the miner to DHCP it means the miner will have to request an IP address from your router, if for whatever your reason your router does not do that you can't access the miner.

So first thing first, make sure your router has DHCP enabled and that the search range on the Bitmain tool covers the entire DHCP table, or even better, get the miner's IP using the router itself.