Are you referring to NiceHash Miner or NiceHash service in general? NiceHash Miner does not support SHA256 ASICs (they can't do any other algorithms, so it doesn't make any sense to support them). But regular connection to NiceHash service (see https://www.nicehash.com/index.jsp?p=software#sha256) should work. Does this work for you? If not, what is the actual issue?

Best regards,
NiceHash team.