i met this before but with 2 situation
1. the smpAdmin has been tried with wrong password more than 3 times, and it will be locked in the next 10 minutes. after 10 mins, it will be unlocked automatically. in this case, log in after 10 mins and it will be successful
2. no idea what happened, i just restarted the server again, and it worked
Rohit, you could try to restart your server and try again.