Hi Parveen, as we've mentioned in the replies we sent you (from our helpdesk and through PM), we've just fixed the server problem which caused the Little Math activation error.
To everyone who encountered the same problem from last September 29th to October 2nd, please do try importing your Little Math license key again and it should work properly now.
If you are still having problems, just write to us again at support[at]brillkids[dot]com
P.S.
As some of you may have noticed, we weren't able to reply as quickly as we usually do especially for messages sent last Sept 28th to 30th. This is because our office is closed on weekends, and coincidentally we had extra 2 days off due to public holidays from Oct 1st to 2nd.