I have the very exact board and the very exact same situation as the originial poster. People who have a similar problem should try another USB port and a new cable. For me that didn't help either.
But the problem with me was, that it couldn't connect as long as a relais board was connected! Maybe that drew too much power?!? Anyway, with just the nano clone connected to the computer and none of mz other parts attached, it connects and I can select the port in the IDE.
I hope that helps anyone who face the same problem.