anandkumar,
Here is the deal, your configuration on the network device is correct i dont know why you are getting fail attempts. Here is what you can do to troubleshoot it:
Try a debug tacacs authentication, log the debug then go over it to see what is causing it.
Since this config looks fine to me i guess your problem may be on the ACS, check your tacacs key, make sure the device is added to the ACS, make sure the users are correctly added on the ACS .
I'm sorry i can help you more