MTP seems to not connect at all to new Nicehash regardless of mining software??
Your observation is correct - I'm also unable to get any mining software to connect to the MTP pool on the new Nicehash platform.
I suppose there are some instabilities on the new platform. It also looks like it's only a small number of miners that moved to the new platform so far. When I'm looking at the statistics on the Nicehash web site there are 10 - 100 times more miner on the old platform.