After asking like 3-4 times, it seems no one on this forum, not even the Developer, knows how to Dual Mine ETH + SMARTCash ( keccak ) on Windows.
Whatever you do or try, Authentication failed, even if the username and password are 100% valid.
Really Really poor community !
We need more information, fellow miner.
But you can start off by illustrating the enitre problem with all the bases covered.
First start off by not mining SmartCash. That probably will help you check whether it is ETH mining problem or a Keccak mining problem.