Your configuration is correct. Recently, Twitter has changed their API and forced to use some complex methods to access twitter. We’ve improved and updated the Twitter counter according to that recent Twitter Api V1.1. So, your Twitter counter should work without any problem.
I think, you have installed the theme just now, So wait for some hours to get the number of followers. Because, if the Twitter counter failed in the first attempt, it will not contact Twitter for some hours. Twitter has API access limitations.
I hope you got this.
Let Me know, if the problem still continues.