Is this an appropriate answer what I have given?

I always get stumped on questions at the end of interview like why do you think you are suitable for this position of senior test analyst which you applied for?

I'm a senior QA looking for change ....this is the question where baffle most of the time and it has become common ..I explain my roles and responsibilities like how I handled the team of junior tester and how I acted for any issues in the team and explaining my skill set as well but I feel the interviewers are not satisfied with the answer I provide. can someone please explain how I should go on explaining and where to highlight?