Without looking at the advert, job description/specification plus what you wrote etc., its difficult to see how any one can be specific in terms of giving feedback as to why you didn't get interviewed.

You should read the job description, person specification and other material carefully and then very specifically address in your application how you meet the requirements of the post. Most public sector organisations provide a lot of information to applicants, including on their webpages. Making a job application is likely a very time consuming process as you have to tailor your application to the organisation and the post. Good luck!